I don't know anybody who uses a tablet PC successfully for general notetaking and data capture.
Digital pens like the io2 are great, but it's true that there are relatively few sources for the dot-patterned paper that the pen uses, and it's further true that the software that comes in the box with the io2 is lackluster. Check out livescribe.com for a very interesting new take on the digital pen. I think this will be HUGE for business users taking notes in meetings.
For situations where you want to capture data from forms instead of "free-form" information, digital pens are great. BSP: check out satorilabs.com to see a forms automation system applied to healthcare.