I think it looks really unconventional, but if they offered pre orders today, I'd buy one. I'm really curious about it. There's no way it could replace controlling FPS, RTS, etc with a kb/m but I wouldn't mind forking money over to Valve. I need a new controller for my PC anyway.
I doubt that. San Andreas and Vice City simply fail to work with any controller I've tried.
The Steam Controller is designed to work with all the games on Steam: past, present, and future. Even the older titles in the catalog and the ones which were not built with controller support. (We’ve fooled those older games into thinking they’re being played with a keyboard and mouse, but we’ve designed a gamepad that’s nothing like either one of those devices.)