Haven't posted in awhile, but I picked up a blue 505 today to replace my 500. I just had to have the latest! A few comments:
Screen definitely has better contrast, but not exponentially so. It is noticeable, but maybe not as great as some people will expect.
Refresh is faster, but similar comments as to the contrast.
It is thinner by a few millimeters and is more square in all dimensions as opposed to all of the slight curves on the 500.
Collections on the card work very well and the alphabetic segmentation of the list view does make navigation quite a bit easier.
The new cover is definitely more leather like. The blue comes with a blue cover and the silver comes with a nice dark tan cover. I wish I could have swapped them around, but they wouldn't let me do that
I'm happy to answer any other questions