@ WIFI lacking...
I might be in the minority in this, but I personally am thankful that the PRS 505 that I have doesn't have any form of wireless, for a couple of reasons.
For one, there's no way that sony can pull an Amazon, er, would that be an Orwell? No way for them to yank media out from under my finger tips while I'm reading it...
Battery life. No wireless sucking juice makes for a simpler and smaller device.
I can also use a non WIFI device at work, whereas we get grouched at otherwise. So the 505 get's carried in a pocket and used whenever there's slow time waiting for something to break, or in transit between jobs.
As for the complaints about the Google books that are only available for those of us in the USA, try just getting them from Google directly, or even from Project Gutenberg. The Sony readers aren't picky as to the format, for the most part. Unlike the Kindle, you can read TXT, PDF, and RTF without requiring conversion to the LRF format which Sony offers it's own books in.
That being said, LRF allows a little easier embedding of images in books, as well as indexing them, but with a bookmark set wherever you're currently at in the book, it's not a deal breaker to read the other formats, just harder to search them.
Finally, if you like Sci-fi, check out Baen.com for their free library and cheap ebooks from the associated authors there. Lots of good works, and even the new books are running at fractions of hardback prices, with older books dropping down into the $2-$5 range, if not to free.
Also, as Andy Baird mentioned, the PRS700's screen was fuzzy compared with both of the 500 and 505's screens, due to the touch screen overlay. I looked at a co-worker's after initially drooling over the idea of it, but was quite happy to have 'missed out' once I actually saw one.