try downloading StepMania if you wanna dance to custom songs. Make your own files or d/l them from sites. if you actually wanna DDR pad DDR to them, make sure you get a usb/Playstation2 controller converty-thingy.... (saw USB2PS/2 on craigslist.... turns out it actually was a PS/2 instead of PS2 adapter... > > ... point is, make sure it's the right one.)
and no. i haven't played this, but i've also heard that it's bad and the steps are random and it's usually off sync. i wouldn't buy it because i don't go for DDR substitutions..(other than SM)...