I don't have a big writeup on 64-bit except to say that we will support both 32-bit and 64-bit development in the Mobile (Tablet) SDK.
So for all none of you who have a 64-bit Tablet, you'll be able to run any 64-bit apps that may be written by developers using 32-bit Tablets. Did that make sense?
I just wanted to keep you posted because a couple of weeks ago, I found a bug that, when traced fully back, was due to a change made for 64-bit.
Don't worry! It's fixed now. I do kind of wish I had a 64-bit Tablet to verify the fix though...<wishful daydreaming>