Gmail Notes (Sidebar add-on for Firefox only) - Mini Review

Basic Info

App Name	Gmail Notes (Sidebar for Firefox only)
App URL	http://gmailnotes.appspot.com/
App Version Reviewed	Current free add-on version 1.5 (Gmail Notes)
Test System Specs	Key Features: Some Technical Details - from here. Quote We're not sure if anyone is interested, but here are some of the technical details behind Gmail Notes. Gmail Notes became technically feasible when Google released Gmail Version 2 in late 2007. One of the great features in Gmail 2 is that each conversation can be accessed by a persistent URL. More precisely, each Gmail conversation has a unique, persistent identifier that can be mapped into a URL. And that identifier can be easily retrieved from the browser and used as a persistent index for each note. To implement our system, we needed three things: A server to store notes online A way to detect the current Gmail conversation A user interface to display and edit notes To store notes online, Google provides another excellent resource in the Google App Engine (GAE) framework, which was first released to the public in early 2008. Applications are very easy to develop using the Python programming language. When uploaded to the Google infrastructure, these applications run "in the cloud". The design of the Gmail Notes server application is based on what is called a RESTful architecture, and we also use JSON (javascript object notation) for the data interface. Unfortunately, we can't point to any good working definitions of REST (we think the Wikipedia entry is disappointing) or JSON, but please trust us when we say that adopting these two techniques made the design easy to implement. And with Google App Engine, it was very easy to get a working note server, which, admittedly, is one of the simplest web applications you could write. As for detecting the current Gmail page, we wrote a browser extension to track the current URL in the address bar. The extensions parses the URL to check if it is a Gmail page and if so, in also extracts the persistent conversation identifier. The user interface is an html/javascript "web application" that runs in the Firefox sidebar. The information from the browser extension is passed to the sidebar application, which connects to the Gmail Notes server to retrieve notes from the online datastore. That's all you need to add notes to Gmail. If it is that easy for us, it makes you wonder why the folks at Google won't take a day or two to put their own note feature in Gmail...
Supported OSes	Firefox only
Support Methods	Built-in feedback system Email
Upgrade Policy	Automatic free upgrades.
Trial Version Available?	Yes. (The production version)
Pricing Scheme	Freeware

SCREENSHOT OF APP INTERFACE: the tabbed sidebar
There are 3 tabs:

About: about the sidebar and room for feedback.
List: List of notes from the server.
Note: displays the note for any given email in your Gmail viewing window

Introduction + Overview: What is Gmail Notes? - from here.

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Gmail Notes is a web application for attaching private notes to your Gmail. With Gmail Notes, you can create a note for each conversation in your Gmail account. You can make a note to, for example, summarize the key points in a long conversation thread. Or to outline some thoughts for a follow up email or phone call. For a list of more ways to use Gmail Notes, see our Typical Uses page.

To use Gmail Notes, you start by installing a Firefox extension which places the application in the Firefox sidebar. You can see Gmail Notes in this screenshot. And you can get more info at our Getting Started page.

You can then connect to the Gmail Notes service using your standard Google account name and password. When viewing a Gmail conversation, you can view/edit an existing annotation in the sidebar, or you can create a new one. One note can be saved for each conversation in your Gmail account. The app provides a rich text editor so that you can highlight text, create lists, include links, etc. For more user interface details, including some screenshots, look at our Everyday Use page.

Gmail Notes is not an integrated feature of Gmail, but a separate web application running on the Google Application Engine Framework. So your notes are stored separately from your Gmail data, although they are still in the Google infrastructure. And as a separate system, there are certain things that Gmail Notes cannot do. It cannot, for example, highlight which messages in your inbox have notes attached to them; you can easily do that using labels or Gmail superstars, but you will have to do it manually. There are other limitations listed on our What It Doesn't Do page.

Gmail Notes is a free service open to any Gmail user.

Who this app is designed for: Where Gmail Notes Are Used - from here.

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Some people are thrilled to learn about Gmail Notes and can't wait to start using it. Others are left wondering what the big deal is about adding notes to Gmail conversations. If you are in the latter category, and are curious about what we use Gmail Notes for, here are the top dozen or so reasons. In no particular order:

Newsgroup digests: (Believe it or not, this is the original reason we developed Gmail Notes.) Many of us receive daily email digests from newsgroups of interest. Each digest might have 2-10 messages, most of which aren't of interest, so most digest emails get deleted. Once in awhile, however, there is something good in a digest that we want to keep it for future reference. By attaching a note to the digest, we can remind ourselves why the digest is important to us and identify the specific messages that are relevant to our interest.
Important emails: Just like newsgroup digests, some emails contain "good stuff", that is, information that we can foresee being useful at some point in the future. In those situations, we like to add a note reminding us what is in there that caught our attention.
Attachment info: Sometimes email is used to send one or more files from one person to another. In many cases, the sender doesn't do a good job identifying the purpose or describing what the files are and/or why they are sent. So when the subject line says something like "Here it is", we will add a note with more descriptive information, like "Attachment is the template file to use for all new web pages".
Downloaded file name/location: And if we download an attachment to a Gmail message, we also like to create a note indicating what folder the file was saved or moved to, and/or if we renamed the file. That helps prevent downloading the same thing multiple times.
Login info or hints: When you sign up for some new web service, you typically get a confirmation email and maybe a friendly welcome message. When we get one of those emails, we like to attach a Gmail Note with our login information, or if it is a really sensitive site, a reminder that will let us reconstruct the username and password. (We like attaching that info to our Gmail message so that it goes with us when we change computers.)
Summaries of long email threads: Email threads can get very long sometimes. Once there are more than five or so messages in a conversation, we sometimes add a note with a synopsis of the messages to date. That way, when a new message comes in on the same thread, we can get back up to speed quickly.
Linking split email threads: Sometimes long email threads get "split" because someone starts a new thread in order to avoid sending a big set of embedded reply messages. (Gmail users don't have this problem, since Gmail collapses previous messages.) Since Gmail assigns a unique and persistent URI to each message thread, we can link two threads together by adding notes to each thread listing the URI to the other thread. Not particularly elegant, but it sure beats losing part of the conversation.
Outlining before writing: Sometimes we want to write down some thoughts to review before authoring a new/reply message. Although we could do that as a draft message, we prefer using a note, where we don't have to be careful not to send it by accident. More importantly, with Gmail Notes it is easy to see our outline/notes while we draft the new message. Interestingly, once the Gmail message is sent, we usually do NOT delete the note, because it has some additional information that didn't end up in the message, but we want to keep around for future reference.
Doing before writing: In addition to planning the words to put in a reply, we sometimes create a little checklist of things we should do — people to consult with, papers to read, etc. — before drafting our message. Of course there are other task management software programs for this, but we like something that is tied to the email thread.
Summaries of phone or in-person discussions: Sometimes, instead of replying to an email message, we call the person so that we can discuss the matter in more detail or more quickly than is possible with email. In those situations, we like to attach a note to the email summarizing the discussions.
Incoming fax info: We use a fax-to-email service, so that an incoming fax is sent to us as an attachment to an email. The subject of the fax email only indicates the phone number of the sending fax machine (for example, "fax received from 800-555-1212") and we have to open the attachment to see what the fax. To avoid opening too many files, especially when looking for some particular fax, we attach a note to prompt our memory without having to open the attachment.
Tracking ebay shipments: This might seem a little odd, but when one of us buys something on ebay, he likes to keep track of how long it takes for the seller to actually ship the item, and how long it takes the shipper to deliver it. Although this isn't important enough for him to create a spreadsheet, he does record this stuff in a note attached to the "Congratulations" email from ebay. Go figure...
Afterthoughts: On more than one occasion, we send an email and an hour later say to ourselves "gee I wish I would have sent this instead". Although we can't do anything about the original email, we attach a note with the better idea, in case we get a chance to reply sometime in the future.
Personal reminders: In today's flat world, we don't always know much about the person at the other end of the an email conversation. Sometimes we like to add a note with some personal information, for example, "this came from the guy I met at the last conference who told me about interframe scripting". Although that might be better suited in the Gmail Contacts page, we often put the notation in Gmail Notes first.

The Good:
It works very well, and does what it is designed to do.

Limitations: What Gmail Notes Does NOT Do - from here.

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Gmail Notes is called a basic annotation system because it is not an internal feature developed by Google, but instead is implemented by external software that infers the current Gmail conversation from the URL displayed in the Firefox address bar. As such, our app does not have access to your actual Gmail contents. For this reason, Gmail Notes is not, and probably will never be, a slick Web 2.0 application. Nevertheless it does provide a basic annotation feature, which some of us think has been missing from Gmail since the beginning. With that said, there are certain constraints that Gmail Notes users must live with:

You can only use Gmail Notes on Firefox browsers versions 3.6 and later. Although we have considered adding support for Gmail Notes on Google Chrome, right now there are no specific plans to do that. (The major obstacle is the limited user interface options available to Chrome extensions.)
Because Gmail Notes is a separate service, you must sign into Gmail Notes separately from signing into Gmail. Fortunately, the Gmail Notes sign-in page has a "remember me" option, so you won't have to do this every time on a trusted system.
In Gmail "threadlist" views, such as the Inbox, Starred, and Sent Mail pages, there is no way for Gmail Notes to know what conversations are displayed in the current page. For this reason, our software cannot highlight or in any way indicate which items in the list have existing notes. That is why we strongly recommend users manually identify those messages using the Gmail Superstars feature.
There is also no way for Gmail Notes to find out when a conversation is deleted. So if you delete a conversation without deleting the note attached to it, that note will essentially be "lost" in the Google cloud.

How it compares to similar apps: Alternatives
See list here: Why don't you just do this [fill in the blank] instead?

Why I think you should use this product:
This tool replaces a sort of "missing link" in Gmail.
My experience from using it in a small way over about 12 months is that it fills a handy niche that cannot otherwise be filled. (See Where Gmail Notes Are Used, above.)
You can make RTF (Rich Text Format) notes related to any specific email/thread. The notes can include (for example) links to Google calendar, Google docs references, or other web sites.

Conclusions:
Very useful for those who could make use of this sort of tool, though usage is evidently low, so maybe not many people can make use of it or need it.(?) (See Gmail Notes reaches 3rd anniversary, below.)

Links to other reviews of this application:
From Gmail Notes blog - here.

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March 10, 2012
Gmail Notes reaches 3rd anniversary
So Gmail Notes has been online for over 3 years now, first going live on March 4, 2009. Back then, we considered our app a temporary workaround until Google added the same feature to Gmail themselves. But now, we now wonder if Gmail will ever support private notes for users. Judging by the extremely small number of Gmail Notes users, there just isn't any serious demand for the feature. Here are a few stats to back that up:

After 3 years, the Gmail Notes servers are storing 8304 notes created by 1575 users, for an average of 5.3 notes per user.
The median, however, is well under 1 note per user, since two-thirds of users (1001) have just a single note in the datastore. Obviously, most people who try Gmail Notes don't continue using it.
On a typical day (Feb 29, 2012), 1842 api requests were made from 24 unique users.
And in the past 30 days, 163 unique users have signed in to Gmail Notes.

(FYI, there is also one Gmail Notes "business" user that pays for an extended quota, but their data are not included in the above stats.)

This low usage is surprising to us since, as the app authors, we cannot imagine using Gmail without notes. Nonetheless, we are glad that only a few people use Gmail Notes, because that allows us to continue providing the service at no cost. So although we originally implemented Gmail Notes as a temporary substitute for a Google-provided notes feature, we now expect that our app will be around for a looooong time...