Wow, I guess I am the only dissenter here....
I can't stand Amazon. I used to love them for many of the same reasons you choose, but I have since learned to hate them for the following reasons:
- Few, if any, items they sell are actually sold by Amazon. Instead, they are a gateway for other stores, not unlike Ebay. They do not, however, generally make this obvious or well known.
- Frequently when I tried to order something that is supposedly in stock, I get confirmation, then, a few days later a cancellation because the object wasn't in stock. I realize this isn't directly Amazon's fault since they are not the store, but it is problematic when you are trying to find and buy a specific item - I mean not so much as an email asking how to proceed, just a flat out cancel!

- Lastly, if you are looking for information about something, particularly technical or specific details, you might as well go somewhere else - you won't find it here. It is a search to find something that *might* fit, then another search (via google) to find details, then a search back at Amazon just to buy it from someone else. For all that annoyance, I will just go to the manufacturer, find exactly what I want, then Bing or Fruggle it to find the best price. If Amazon happens to be it, good for them, but I am no longer looking there.
Enough of my rant though, I do see what many see in them, particularly for books and/or music. However, I rarely buy these items and if I do, it is rarely online. Those are impulse buy types of things for me. So as for me, adios Amazon....
-steeladept
Must be a different Amazon to the one I am used to ...
Every listed product says "Sold by ..." near the top of the page and I would say that 95% of products I have looked at (that are still in production) are sold by Amazon (at least in the UK).
I much prefer Marketplace Sellers on Amazon to eBay simply because Amazon actually do support the customer if something goes wrong (rarely in my experience and you look at the seller ratings). I have used the A-Z guarantee on a few occasions (over the last 10 years) when something hasn't turned up in the quoted time frame and Amazon have refunded the money without question usually within 24 hours and with a grovelling apology.
No shop site has 100% accurate information on every product but I do find Amazon has a reasonable description and technical info on products and if they get something wrong it is pretty straightforward to get it corrected.
I am not an apologist for Amazon but I do find Prime delivery in the UK is pretty impressive (eg. I ordered a box set of books yesterday at 7pm, it was delivered today at 2.30pm - 19.5 hours from placing the order to getting it in my hands). They are also the only seller I have ever come across that will send out a replacement for a faulty item whilst waiting for the damaged item to be returned (damage usually caused in transit or the fault of the manufacturer - eg. I bought a laptop and the touchpad didn't work - I had the replacement within 24 hours and they sent a courier to collect the faulty goods on a day of my choosing).
They aren't perfect by any means but they make a good stab at it and are prompt with customer support (even calling you back within a few minutes when you ask them to online).