Stepmania is such a robust program with its low hardware requirements and its enormous collection of simfiles that it really would be stupid not to get it with a USB pad as an addition or replacement to the ps2/xbox versions. Heck, the newer version even supports widescreen displays so your arrows don't get all stretched out.
The one thing that's starting to annoy me about DDR's new stepcharts....which first was evident in supernova, was that songs like fascination MAXX and the super love me mix were tossing steps at you that seem to be a lot more doable if you have the handle bar, such as those quick successive jumps (you can use the bar to bring yourself to the ground faster). I normally play with a hard foam mat (if you treat them correctly, they last you years!) and not having that handle bar support makes it really hard to be able to do those kinds of steps. You just kinda BS through them though and take your B or C (especially towards the end of fascination super love me mix on challenge) and play something that's more fun. The other annoying steps are the superfast (350BPM+) crossover steps that again seem to be geared towards bar usage for support. Twisting one's torso without the bar that fast is just asking for something to snap.
If you want some excellent ITG style step charts, you should look into Ike Pie's stuff......those are really great steps (Sounds of Life on challenge is ridiculously difficult though)! The only annoying thing is that Gunther is in the song selection more than once. There's also this 13 footer version of IOSYS Overdrive (from this guy rob0090 or something like that) that's a tough one to get through, but fun nonetheless. I really wish that there were more stuff on stepmania from DJ sharpnel or Onoken.
In my opinion, the best way to play, if you don't want a metal mat, is to place a hard foam mat on a plywood or particle board surface....which is something that you can get cheap and custom cut for you at a hardware store. 40x40 inches should be fine, and buy one of those nonslip carpet runners to put under the wood surface as well as between the wood and the pad (if your pad's grip sucks). I've also found that a lot of hard foam mats are crap because they have such a mushy insert in them (they're about as hard as a microwaved pizza crust....mushy as hell). If you can get your hands on one of the redoctane ignition pad inserts, you can use that on other hard foam pads and they work like a dream. I have to admit though, it's kinda hard to find a good DDR mat nowadays. Getting one is taking a shot in the dark.
I'm actually still looking for good songpacks with well designed stepcharts in the ITG 11-13 level. If someone has some they're willing to share I'd love to know about it. Send me a PM or something!
