The Music Channel definitely sounds cool (especially if it somehow works with the new Virgin Radio that was just announced http://www.evilavatar.com/forums/showthread.php?t=28265&
If they make this Health Channel fun, it could be very useful. I actually tried the Wii Play health stuff for a while, but it didn't really inspire me to continue. I get the impression, however, that the HC will be a little dry and boring. Not sure what gives me that impression, but it's one I have.