The long delays and waits are almost over, Street Fighter 4 for PC is being release in the UK any day now and is already available online. The PC version is going to be able to play with other PCs over live as well as xbox 360s(confirmed myself, the xbox live settings include a crossplatform option).
The game includes a controller mapper that lets you use the keyboard or any standard controller, you assign the buttons on the pad to the various functions of an xbox 360 pad and then the controls are configurable in the game also, swapping around the xbox 360 functions. Quick warning though, people may want to to buy two of the same kind of pad if they want to multiplayer on one machine, as the controller mapper maps the same buttons to every player, this may be overcome using xbox 360 controllers, but I haven't been able to test.
The game includes a controller mapper that lets you use the keyboard or any standard controller, you assign the buttons on the pad to the various functions of an xbox 360 pad and then the controls are configurable in the game also, swapping around the xbox 360 functions. Quick warning though, people may want to to buy two of the same kind of pad if they want to multiplayer on one machine, as the controller mapper maps the same buttons to every player, this may be overcome using xbox 360 controllers, but I haven't been able to test.