I think MS is in a "damned id you do, damned if you don't" situation with regards to the motion sensing.
If they do incorporate it into their system and games the Nintendo fanboys will lambast them for jumping on the bandwagon, but if they don't they will be forever criticized as being "last gen" in terms of gameplay.
I think we should learn from the example of games like Lair, and not force the control scheme into situations where it doesn't work well. I'm all for Wii Sports, but I can't imagine myself having fun with the motion sensing anywhere else.








