Yeah, the only problem with the Steam controller is that your computer needs to be running Steam. It also needs to be in the most invasive, resource hogging mode possible...You have to be in Big picture mode.
I am not going to support their software+hardware vendor lock-in. There is no reason they could not have made it an independent application Like Pinnacle profiler, or Xpadder. On Day 1 their biggest competition, the Xbox 360 controller, already is more versatile, and use-able. You just need a driver running and you can use it for any controller enabled game.
The Cool thing is that steam controller has an Xbox 360 emulation mode. So If I make sure my game works with the Xbox 360 controller, it is already supported by the Steam controller.
It would be a cool item in the C2 feature list though, I defiantly think Scirra should see if they can directly support it.