I bought the 505 and it does exactly what it says on the tin and I am happy for it to do so. I have accumulated some 40Gb of e-books mostly in pdf format that I otherwise am unlikely to read in a lifetime of sitting on front of a screen but now can read on the train into work - result!
As far as touch screen is concerned I want to look at a pristine e-ink screen when reading , not one with the thumb-prints from my last slice of buttery toast all over it.
And Wi-fi ? Don't need it, don't want it...all you Kindlers are welcome to it especially after the recent furore over the unauthorised deletion of paid-for material. And aesthetically, a colleague has just bought a Kindle (in the UK) and has already admitted "it doesn't look and feel as good as yours" having tried my 505 before his Kindle arrived. OK no margin note facility, but I haven't made margin notes in a book since I was a student 35 years ago so I ain't gonna start now.
And best of all, my Sony 505 was £150 from play.com which is about the price of 4 technical 2" thick books and I have several hundred stored electronically that I can carry around without needing a suitcase to hold them in.
Want an e-book reader?, get the 505 -- you know it makes sense!