[kulaga]

I took advantage of the trade-in offer to upgrade my 2 year old PRS-500 to a shiny new 505.

1. The background of the 505 is a crisp white vs the light gray of my old 500. Makes a difference, but not a reason to upgrade alone.
2. The page refresh is noticeably faster, I no longer need to press the page button then read the last sentence before it refreshes. Just a slight increase, but it makes a big difference
3. Listing books by author, title or date takes you to a second screen that divides the alphabet and lists the number of books in each division. No more pressing the page button 19 times to scroll through all the books (I'm a bit of a pack rat with my reader and SD card).
4. Ability to delete books from the reader. I love this. After I read a book, I transfer it to the memory card (would love to do this from the reader) and frequently forget to delete the copy on the reader. Now I can clean things up without searching for the USB cord.
5. Accidentally pressing the numbers buttons will no longer take you to a random place in the book. Instead, you use the buttons to enter the page number you would like to go to. No more cursing and going back to the history to figure out what page you were on.
6. Cover is stiffer and nicer than the old one, however my Verilux light fits looser (still usable but need to be careful when carrying).
7. I finally get used to holding a "book" in my left hand and they switch the buttons to the right. Not a big deal, but takes some getting used to.

Overall, I'm very glad I upgraded. There was no killer feature for me (I avoid PDFs whenever possible), just a lot of small refinements that improve an already great product.