I've owned and used a 3650 for going on 3 years now, and it took me most of that time to figure out that not only is the round keypad "not that bad," but I'd be prepared to argue that it's actually good -- if not better -- than your average square keypad. You can call me crazy, but the reason is simple: the round keypad offers a one dimensional search space for numbers and letters:
Rather than having feel and count the possible subtle lines that separate buttons on most phones and remembering that "T" is sort of bottom middle and "2" is top middle unless there are extra buttons above it, I just have to remember that "T" is near the end and"2" is near the beginning. In fact, I wouldn't even call it a "round keypad," because it's actually a linear keypad.
In addition to the linear, one dimensional search space (the same one that make's the Mac's menu bar so much nicer to use), each of the non-numeric keys have distinct shapes and positions. Where there are repeated shapes, they're on opposite sides of the phone, and serve opposite purposes (answer and hang-up, edit input and delete/clear, select and back/exit). Recognizing that different button shapes help the thumb find what it's looking for was one of the main differentiators that made the GameCube controller so great.
(Of course, off the deep end of different button shapes are the many many other Nokia phones that Beattie was actually talking about.)
I admit the keypad had a bit of a learning curve, but once learned, if not better, the 3650's keypad was at least as good as your cookie cutter keypad. It's too bad most people weren't willing to give that different looking thing a chance; When I finally upgrade my phone later this year, I for one will definitely miss that quirky looking keypad.