My personal experience with Amazon over the past year has been very positive. I have a Kindle and IPONE reader. I use them both extensively.
The big difference with the Amazon ebook process is they maintain your copies for you, you can down load them to the device of your choice when ever you want by logging onto your account. Laptop, Desktop, IPHONE etc. The only DRM they apply is by the account. Once you purchase on your account, you can read it on any device as long as you log onto your Amazon account with that device.
Also they have a kind of loaner capability that I have not used. You go through a simple process to loan it to another account holder and they can open it. Only one account can open it at a time and after some interval it goes back to your account long term
One advantage is that Amazon maintains the data for you so you dont have to have your own library with all the implications for maintenance, backup etc.