I purchased the Sony Reader 505 and the Kindle - and kept both! I was unable to part with either one. I find the 505 easier and less bulky to tote around in my purse and basically easier navigation when not reading at home. If I were forced to give one up - well, let's just say they'd have to kill me and pry them both out of my cold, dead hands!
True confession - I still buy pback books, although not nearly as many!
What????? A girl can't have it all???