I can see an Android-based tablet being a viable alternative to the iPad, but a Win7-based tablet? nope.
I agree!
I think its been said before and some of the comments here are reiterating it, a tablet will only succeed if its designed from the ground up to work as a mobile, touch interface device from the get go. You can't simply take an full on computing OS like Windows 7 and stick it into a mobile touch device, it just won't work very well.
This is why I think Apple has not worries about windows based tablets.
Yet, the android tablet is something that will be based on a mobile OS that uses touch. Given that, it will run far more smoothly and have a much better user experience. If Android OS continues to grow and get more and more apps, I see an well made, sleek android tablet being a real competitor to the iPad in a few years.