*January 7th, 2005 was the day I stopped caring about Mario*
Good use of Mario, nice to see Nintendo recruiting more third party support, yadda yadda yadda. In spite of that, I'm not spending $500 on games just because they have Mario in them this year. As far as I'm concerned, chasing the NBA announcement with this one qualifies as "jumping the shark". Now instead of being motivated to buy games I didn't care about until they added Mario to them, I suddenly feel free from the desire to own any of them. I'll never have a complete Mario collection, so there's no point in wasting my money on any of the spin-offs anymore, including the decent ones like Mario Golf.
Still a nice announcement, but I thought Mario was already overexposed in 2004. If I buy this game it will be because I'm intrigued by dancing games, not because of Mario.