I was very happy with the PRS700. The screen didn't bother me and I found it a step up from the LCD on my EBW1150. It reads PDF beautifully and is fast, and the side lights are great for reading at night.
Having said that. If I had to do it again I'd buy the 505. My 700 has been at SOny for repair for over a month now. The 505 doesn't seem to have the dust issues, plus everyone raves about the screen.