I have a 350 and, as others, love it. I actually had a 6" reader first, thinking the 5" screen would be way to small. Bought a 350 for my daughter though for the portability (very handbag friendly). Played around with it for a couple of weeks before Christmas (hey, it's my goddam duty to make sure the presents I give work properly!
) and much to my surprise I found it very user friendly and "old eye"-friendly. The screen clarity is amazing, and the crisp letters are just what I need for good readability.
So, sold my 6" and got a 350 instead. I'll probably get a second reader with a larger screen as well to use at home when a somewhat chunkier device wouldn't be problem. What to get? Who knows...
Oh yeah, forgot an advantage with the smaller screen: The light in my lighten cover actually lights up the whole screen. Makes it extra useful!