You're right, a real tablet needs a different os and a different metaphor for interaction.
For example, most people are probably going to be single tasking on a tablet, but still want multiple tasks open at once. Surf the web, but have your im in the background to pop up when you get a message.
Get rid of the menu bars and task launchers that are always on teh scrieen and make use of the types of input you have available. For example, tapping with three fingers at once (just like hitting ctrl+alt+del) could bring up the launcher menu. Like hitting ctrl+esc or the windows key in windows.
There are already gestures, like finger down to page down or finger across to turn a page. Just make using two fingers swap between running tasks, like alt+tab. Or take advantage of the fact that most people will be holding the tablet with two hands and make use of tabs on opposite sides of the screen at the same time be a gesture.
I'm writing this on laptop with a swivel screen and when I put it in pad mode, these gestures are there. Problem is that because I bought the really cheap one, it is far too heavy to use as an actual tablet. It takes two hands to hold it comfortably.
I keep thinking that I want a tablet that will let me read, surf, watch video, read email, videochat, and do some basic typing(just turn it in landscape mode and bring up a translucent qwerty keyboard as big as a regular notebook keyboard). All seem to promise they can do that, but they aren't quite there yet.
Maybe its out there, but it isn't getting the press that the ipad has.