I'm supposed to be getting a tablet PC (convertible) sometime soon for work, and I've spent some time specifically considering just this point. I've also been playing with Microsoft
OneNote (came with my wife's install of Office 2007), which looks very promising for note taking/organizing.
What I've come up with is I think I'll keep using paper for quick notes that I don't expect to want more than a few minutes to a couple of hours, and probably do OneNote notes for to-do lists and things I need/want to keep longer. As I expect to be traveling more for work starting this fall, it'll be helpful to reduce the amount of paper I'll have to keep up with.
As I see it, the drawback to e-notes is having to decide where to put them on the PC so that I can find the things later (slows things down you understand). OneNote helps with that (I find its interface quite intuitive, and takes care of storing and retrieving notes automatically), but for really quick stuff, I think paper is going to be a better solution.
As for ways to get hand written things digitized, I think something like the
G-Note tablets could be a good complementing device for that purpose, depending on what you're wanting to do. It would seem to be workable for whatever computer otherwise fits a person's needs, from UMPC to full-tower desktop.