I just got my HP Compaq tc4200 on Monday and I love this thing. I've played with HP tablets in the past (tc1000), and this is heads and shoulders above that system.
First, I love the hybrid notebook/tablet approach. I know Toshiba beat us to the punch on this one, but I'm glad we had enough sense to follow suit. Handwriting recognition is great - definitely a lot better than the first release of Windows XP Tablet PC Edition - but the fact of the matter is I can type a whole lot faster than I can write. On the other hand, being able to read, annotate, and highlight PDFs, Presentations, and other docs is awesome. This is definitely going to see a lot of use for my next two years of grad school!