Even if the keyboard + mouse is superior, I have never really liked it. I was playing FPS on the PC before Halo and the duel analog revolution on consoles. I just don't find it anywhere near as enjoyable. RTS on the other hand just trout all over a controller.

I will wait on big picture mode until it is actually released because most games I have for the PC, I can play on the TV. I am playing Borderlands 2 with a controller on my TV with Steam. Works great!