I played one at Christmas with the family and it was great fun, the sports game was really good and got everyone playing/involved. I find these things are boring on my own though, really needs a small crowd to get the most fun !
I don't have an xbox myself though, got a ps3 - it's version of this is supposed to be better than Kinnect (according to reviews) but the PS3 doesn't really have any good games yet. Though some decent ones are in the works I think.