This is a space Microsoft has been no good at before. To be honest, I really don't know if I want Windows on my Slate. I would like it a bit better to manage documents on it and edit my work documents from a Slate, that would give me a great deal more mobility. But the simple iPad/iPhone/iTouch UI seems to be just about right for a small device. I would have just a larger version of windows mobile.
I guess the key point is that Microsoft should probably come up with something other than Windows for getting small. Microsoft messed up on mobile because it needed to keep using Windows.