I have partially switched to an HP tablet - the 2710p - because of the ability to use MS OneNote for my research. The experience is interesting - the combination of tablet input and OneNote is really powerful and ideally suited to a research scientist. However, the underlying Vista OS drives me crazy, and makes me wonder whether to give up trying. I still use an iMac for all my main work, and still go back to my 15" macbook often because I don't trust the HP.
The handwriting recognition system is amazing, though, on the HP tablet. All my handwritten OneNote notes are indexed in background so they can be searched, and I'm astounded at the software's ability to recognize my appalling handwriting. And input is generally very high accuracy - it's impressive. Life would be better with a combination of stylus and touch, though (the HP has a pen-only screen), and some changes to the OS which would help pen & finger-based operation. But the handwriting recognition is surprisingly good - years of Palm and Windows Mobile supposed recognition had left me jaded, but the vista version is quite something.
So, in some ideal world, I'd like a mac tablet, please, and a port of OneNote to OS X by the Mac BU at MS (if you've never played with OneNote, go try it out - it's part of Office and it's the only piece of microsoft software that I've ever admired)