I have a Thinkpad tablet. For the most part, I don't use the pen on my screen when it's in laptop mode. Just isn't worth the extra step of moving my hand away from the keyboard. The other reason is that it's tough to use a pen on an upright screen. Just imagine trying to write or draw on your wall.
I only use the pen when the laptop screen is folded down into 'tablet' mode. Much easier to use when it's like a notepad on your desk.
Maybe if there was a big UI change or great killer app that need touch screen capabilities OR they get as cheap as normal screens), otherwise I don't see touchscreens getting that popular. Right now, I could only imagine using a touchscreen to 'click' to close/open applications and select items. They do use touchscreens in retail/restaurant industries, but they're very simple interfaces.
Windows XP Tablet edition supported tablets/touchscreens. Then Vista integrated support for it. I'm using Vista on my tablet. I'm curious on how W7 improved over Vista, except maybe better handwritten recognition. Wonder if they have multi-touch, which is 'patented' by Apple.