[This post goes a bit beyond the topic, but by coincidence, I just had to deal with EN 2.2 and the Portable Version.]
I bought the Evernote 2.2.1 bundle (Desktop/Portable) shortly before 2.x was discontinued (edit: more precisely, Dec, 2007).
By that time, there was no "Plus" version anymore, just a free and a registered version (maybe the free one had a demo period for the advanced features, can't remember). I got the registered version after purchase as a separate binary, no unlock key needed. The portable version had some features missing. IIRC, there never was a free portable version, nor a trial.
However, I must admit that I never really used either one (played with the desktop version for a while, never even installed the portable one). Until now, that is.
I'm not too thrilled with the concept of EN 3.x, but I needed a good notetaking tool, so I remembered this app.
While the desktop app works almost as intended (OCR in images doesn't work too well, but maybe that's only a problem with German, and the UniClipper floating window is missing on my machine), I had a bumpy trip when finally trying the portable version: When running the setup exe, I immediately got a virus alert from Comodo Antivirus (please don't ask): "Heur.Pck.MoleBox". After uploading the setup file to VirusTotal, I got a total of 4 positives (out of 40; interestingly not from Comodo, this time), mostly also pointing to MoleBox (why do some AV developers have to come up with totally crappy virus/trojan names like "SuspiciousR-Mytob3" [eSafe] or even "Artemis!73589BAB276A" [McAfee's Artemis]?). I took these as false positives caused by the use of MoleBox (of which I only remotely understand what it does) and decided to continue.
Then, for whatever reason, the portable version wouldn't install on the stick when I tried it on my Tablet (Motion LS800, XP Tablet 2005 SP2). It installed on the stick when I tried it on another desktop machine. But then, again, it wouldn't run on the tablet. I have no idea why it refuses to run on exactly that machine. The desktop version does run on it.
FWIW, this is what the help file of my desktop version (188.8.131.526) says about the portable version:
Because of the registry-less nature of EverNote Portable, the current version has certain limitations, particularly in the way it interacts with other desktop applications:
1. It does not include EverNote Web and Email Clippers for Internet Explorer, Firefox, Outlook and Thunderbird. However, if EverNote Clippers are already installed on the computer where EverNote Portable is used, it will be able to use such installed Clippers. In general, EverNote Portable relies on the Universal Clipper to capture content from other applications, as explained above.
2. Links between notes and from external applications to notes are not supported in EverNote Portable.
3. The Windows TEMP directory is used in certain cases, so users must ensure that they have sufficient privileges to write into it.
Note: Synchronization, advanced digital ink features, and search in images are not available in the Portable version."