I stopped by a SonyStyle store on my way home and played with the 505 for a few minutes. Here is my impression:
1. The screen:
It has whiter background and no ghosting. Refreshing a little bit faster but not much. The refreshing routine is different, and seems to have one more step which displays fuzzified reversed contents of current page which I found quite distracting.
2. The cover:
The cover is looser and has more margin on the right side. I think I like the 500 one more which has better fit and feels compact in your hand. There is no point to see the back of the unit which is quite unsightly. They should just relocate the reset hole.
3. The form factors:
The 500 has curve edges and memory card cover and a slicker look. The 505 has all staight edges and no memory card covers, and looks quite rigid and cold. The 505 is a bit thinner but not by much.
4. The buttons:
The 505 has moved page buttons on the right and I found it not easy to control because of the shape of the edge. The joy stick is replaced by the dial pad which can be controlled more accurately.
My impression may be biased because I am still in love with the 500
Overall I like the 500 form factors better and the screen alone is not compelling enough for an upgrade. And I can't live without the clock since I tend to forget time while reading a novel
