I use a Kinesis Advantage. I have two of them actually, one for home use, and the other as at the office. I honestly would not have a job without them. I destroyed my wrists on that crappy Apple keyboard. It's awful for your wrists and gave me crippling RSI. If I use a laptop for more than an hour or two, I'm going to be feeling it later.

I've never tried the datahand. I'd love to but, my understanding is that they're super hard to find and very expensive. Also, there's a stigma that goes with weird looking keyboards. I always get comments about mine. People definitely prefer aesthetics over preventing an RSI.

Developers, protect your hands and wrists and get a GOOD keyboard.