I just got a 350 and have been LOVING that my eBook template's links (that I convert almost all my books to for consistency) work with just a quick tap on the screen. In longer lists of links all together I sometimes dig out the stylus to get an accurate click on the proper link I'm aiming for, but generally I don't even need to do that. Loving it. (I'd been about 2 steps from just removing all the links in my template as my Hanlin V3 didn't bother even letting me use the links in my ePubs - it would let me use them in some other formats, but not ePubs at all.)
I haven't played with the 650 much at all, but I know I love the 350's touch screen - except when I want to plunk the reader into a ziploc baggie and read in the tub, the touchscreen is used for so much and is IR so doesn't even fully require taps, just an object passing suggestively close, to activate it, I can't read with it in a baggie like I can with my old reader. Good thing my old reader still works for that
(the things you don't realize are important can end up being a hassle in the end sometimes, so thought I'd mention it...but maybe I'm the odd duck here
).