After a hands-on with the 700 at the SonyStyle store in Phoenix, I traded in my 500 on the spot for a 505.
I'm really mostly excited that I can now check out books from the library and put them on my Reader, something the 500 couldn't do. After playing with the 700, I decided the somewhat flaky touchscreen and uneven frontlighting wasn't for me.
I was also super amused that the Reader Revolution guy tossed his 505 like a frisbee against a wall and then proceeded to drop it waist high onto the ground and picked it up like nothing happened. Not a nick, scratch, or dent on it and it worked perfect as always. Not for the faint of heart (or me), but a pretty impressive demo of its durability to be sure.