I agree with the OP, Sony has been de-evolving ever since the 505. I bought a 600, returned it and "downgraded" to a 300. Returned that and "downgraded" to a 505 for $185 brand new and boxed off Craigslist (No $70 Target steal, but not bad). I am of the opinion that all this "downgrading" has left me with the finest reader Sony makes.
For my money, the 505 easily trumps the 700, 600, and 300 on what are the two most important qualities for an ereader: Screen quality and general readability.
SCREEN: The 505 has the best screen of any Sony reader. Hands down better than the 700 and 600. No glare issues, far better contrast, no contest. The 300 is just as sharp and glare free... but only five inches, making PDF's a chore.
READABILITY: The 505 has the best reading ergonomics. Or should I say the 505 has reading ergonomics, the 700, 600, and 300 do not. The swiping gesture for the 600 and 700 is awkward, and often needs to be repeated on the unresponsive touch screens... and the 300's center page toggle is neither here nor there, but in sort of a right hand/left hand wasteland for most reading positions. The 505's lower left page toggle is perfect for the thumb when holding the reader single-handed like a paperback, and the two right edge buttons hit the thumb perfectly when holding the reader in a traditional two-handed grip. It is true that the 600 has faster page turns than the 505, but any small gain in software speed is negated by the fact that the physical action required to turn the page is slower than the 505... so the 505 actually has faster page turns overall.
There's no denying the 700, 600, and 300 beat the 505 in terms of storage. But I believe storage on most current media devices is a selling point more than a tangible concern. Who needs 160 books on their reader, let alone 350? And if you somehow do (perhaps you're planning to be marooned for three years on an island with no computer but a palm tree with an electrical outlet?) then you can get an SD card for 20 bucks that will let you store thousands of titles on the 505...
As for the dictionary on the 600... that may be important for some folks. Not me.
Last edited by Starter; 11-11-2009 at 08:05 AM.