Personally, if there was a device like either GeraldKo or ekul described, I'd buy it right now, no questions asked (well maybe 2 or 3).

I'd like to add removable battery as a nice option.

Stylus is mandatory. From what I've read, capacitive touch screen don't really have the resolution needed to fulfill the role of a tablet. It'd be difficult to annotate pdf's in xjournal or manipulate a spreadsheet in gnumeric or make quick sketches/handwritten notes, and on and on. I don't think it would be possible to accurately hit links on webpages at a viewing level that puts most of the page on the screen (like I can do now with my stylus).