This is beyond awesome. If you've not heard of it, imagine DDR, but with 5 panels arranged in a sort of X pattern. It's been around for about as long as DDR, and it's definitely quality shit. Here are some relevant URLs for the interested to drool over:
Mastiff web site
Official press-release
IGN's preview
Gamespot's preview
The game will be released for PS2 and XBox around summer. Meanwhile, I'll be foaming at the mouth.