You want to try to figure out the UI of the RAT [Rumored Apple Tablet]? Go get yourself a comic book, or any other rectangle that measures roughly 10” on the diagonal. Hold it as though you’re reading what’s on the surface.

You see the problem? Your fingers get in the way. Think about how big that surface is, too. That’s a lot of acreage to scan, looking for the right buttons to push.

While you’ve got it in your hands, imagine that it’s a sheet of thin steel. That’s heavy, isn’t it? Hard to hold up for long periods of time.

Think about how a user interface would have to incorporate those observations. Now imagine that you’ve been doing this experiment for four years and not four minutes.

That’s a very long list of observations. If you didn’t come up with a workable solution, don’t worry: I think Apple has.

This is why I have to circle back to my assertion that here and now, nobody outside of Apple can predict more than half of what the RAT will be about.

Its fun to speculate, and it seems that since John Gruber's speculative post many other smart people have contributed their own wild guesses.

"If you didn’t come up with a workable solution, don’t worry: I think Apple has.".