I used to play all the time at the arcade, but I haven't gotten to go for so long...
I used to have DDR for PS1, and 2 soft mats. Eventually, the game stopped working on my PS2, and both mats broke!
Anyway, then I bought DDR Max for PS2, and a hard plastic mat which I don't like very much. It makes too much noise when you step on it, and isn't the most responsive. Too bad, because I paid about $80 for it, plus $50 for the game.
Most recently, I got DDR Ultramix for Xbox and the soft, non-slip Konami pad that came bundled with the game, as a Christmas gift. It also features online play, and song downloads. (for a small fee...) I've been too lazy to play it much though.