I've been a very happy PRS-600 owner for some time. It was wonderful.
I did, however, have a problem that has, now, ruined my e-reader (for my perfectionist self)
Dust.
Finally, my PRS-600 got a large, large piece of dirt inbetween the two screens. It won't come out, and covers about 2-letters worth of space on the medium/epub font. It's not nice.
If you're considering buying a PRS-600, since there will undoubtedly be numerous sales soon on the now-obsolete reader... Consider carefully. The device is wonderful, but if you're picky about the screen's readability, don't. Many will tell you /they've/ never had trouble, and they probably haven't. I have, and it's not pleasant!
The warranty just expired, too. How unfortunate! It's a very nice device, and I'm sad that mine is now splotched up.
On the plus side, I really want a kindle.
Just thought I'd share.