PRS-650s are super hard to find. I've been watching that ongoing saga on the Sony forum ever since I joined. I really lucked out when I got my PRS-650. I got it with credit card points and I knew *nothing* about the available choices at that time; I just got a letter that the program was ending, use the points or lose them, and the reader was the coolest thing I could get with the points I had. The credit card people didn't even list the model number in their catalog, it was just a Sony Reader. Then I joined this site and learned that I'd gotten a well-reviewed but very hard-to-find item.
Since then my inner magpie keeps making me pick up more of these gadgets. The shiny, it calls to me! But I still use the PRS-650 the most. And I haven't bought a single dead tree book since.