It's not as much fun as real sparring, but playing Tekken on a dance mat is better than nothing. It would be much better if there was a stronger connection between your movements and your character's movements, if you couldn't knock someone out with a punch to the knee, and if there were a referee.
It's really frustrating to not be able to do things in the game that you can do in real life, and being able to do things in the game that I can't do in real life doesn't make up for it. If only Ling Xiaoyu lived round here.
I think that's the first time a computer game has made me sweat.