A tablet PC has a stylus and a touch screen. It'll do everything that a notebook does plus allow you to take notes in your handwriting. Think of it as a modern slate . (Done by rotating the screen as you mentioned). This can later be converted into text by using a handwriting recognition program (may not be 100% accurate). Thats about the only difference. All else remaining the same (config/weight etc), a tablet pc is a better option than a notebook for sure. However most of them will be a lot more expensive than a notebook.
^^Yea exactly. Though most of the time the cpu's you find in tablet pc's are low or ultra low voltage versions to consume less power and give a longer battery life.
yea generally notebooks will be more powerful than tablet pc's. as far as the gaming tablet pc, i have yet to come across a tablet pc with anything other than integrated graphics. But then again im no expert on tablet pc's)