I might have to watch the Dance Central demo videos again (I don't actually care about playing rhythm dance games), but after a second thought, the one for one body tracking becomes a lot less impressive if the animation of your onscreen character is still "canned."
As odd as it may sound, if you can't make your onscreen character dance really horribly by exactly mirroring your own bad renditions of dance moves, while the software may be tracking all your movements, it's still only giving you feedback on the basis of "points" for matching (or not matching) what the game tells you to mimic, rather than showing you exactly how bad your dancing really looks.
It doesn't look like the Kinect software currently allows for 3D marionette style puppet animation (true one for one mo-cap style mapping) where your in game character exactly mimics the player's movements (ie you absent mindedly scratch your nose, your character scratches its nose).
The fact that the yoga game uses a flattened out color silhouette of the player (essentially just clipped scanned video of the player) seems to support the notion that the initial batch of Kinect games aren't quite there yet.
