mouse and keyboard guarantees a niche audience though.
cat friendly controller confirmed
seriously though, Steam's "Big Picture" is all about using a controller. this is from back in January:
So are most of these going to be Linux-based Steam Boxes?
We’ll come out with our own and we’ll sell it to consumers by ourselves. That’ll be a Linux box, [and] if you want to install Windows you can. We’re not going to make it hard. This is not some locked box by any stretch of the imagination. We also think that a controller that has higher precision and lower latency is another interesting thing to have.