Just got mine yesterday. Had the PRS-505 which I liked a lot. This is even much, much better.
Same size screen, but in a smaller, lighter package. Too, I really like the touch screen.
You also get a scribe...you don't need it to read books, but it comes in handy for jotting notes.
Also comes with a virtual keypad so that you can type notes.
The Wi-Fi, dictionary, touch screen, note taker, audio, browser, photo album, huge storage, USB mini port, SD card slot...and so many other treats!
P.S.: Charges through the mini-USB port, connected to your computer. Fair enough...but, I've got to have a stand alone charger (available for $25). I understand...the price would increase accordingly, and this is a very competitive market.
For me, a happy solution is that I realized the same charger for my HTC Incredible phone is a perfect match.
I would still buy it, even if it meant paying extra for the charger. That's how much I like it.