Have been playing this for a couple of years now and still love it. StepMania is far better that the Official Dance Dance Revolution game for the PC, and can easily be configured for any system - plenty of eyecandy if your machine can handle the load.
The obvious problem is that it doesn't come with any songs! But a little searching will soon turn up many to choose from, both from the original arcade games and fan routines to just about any song you can imagine.
I have two soft dancemats (grabbed them in a sale at Dixons for £5 each) and use a twin Playstation to USB convertor to connect them to my PC (got that from eBay). Be warned however that the soft mats do not last that long before the vinyl starts to split and the buttons loose some of their responsiveness. RedOctane do make far superious solid mats, but the price hike is too much for the occasional user. Still you could always make your own...