I just bought one, the xbox & all two days ago. It took a lot of web searching to find the pads, got the box & game @ walmart.com. The PS2 has more versions, but I figured the xbox would be better for other games.
The game has a workout version that lets you count calories burned. I got 2 of the medium priced pads, red-octane pads or metal ones are $100+ apiece. My only gripe with the xbox version over the PS2 version is there are very few easy songs, most of the stuff is INSANE.
The wife wanted an exercise machine so I got this, I figured a bowflex would end up as expensive coat hanger after a while, the xbox will find other uses even if the DDR doesn't get used. Both my 6 & 3 year old girls love it too, I even use it, just to show the wife I'm a better dancer than her. Man what a workout, sweated like a whore in church!