Windows tablets have been on the market for a while now. Apple did not invent the tablet pc format. Granted, they've done well with it - kudos to Apple etc. (I'm not flame-baiting here).
I think Microsoft is in a very strong position to do really well in this market. I remember using my Fujitsu Lifebook (I forget the model) 5 years ago with a stylus for note taking. It had really good integration with MS Office and was very usable. In addition, the OneNote software works really well in a table environment.
What they do need to work on is the multi-touch, gesture type of interface. Menus are not very good UI for fingers
.