Yep...an official DDR game is now out for the PC.
http://www.konamihwi.com/DDRPC/index.html
This took me by surprise, quite frankly. And it came out on my BIRTHDAY, no less. What a present. ^_^
And as for the music list, it is NOT the same as DDR USA for the PSX, in fact it seems to borrow a lot of songs from Konamix as well.
If you want to snag your own copy though, it's gonna be a little tough. You can either get it from
http://www.outpost.com/product/3293531
or a store called "Fry's"
There is also a converter for if you want to use your own pad with the game.
http://shop2.outpost.com/product/3052389/
There is an additional section named downloads. New charactors for download are confirmed, but perhaps they could add more music through that as well...