I mean, this is really the best combination for most character controlled games and is, in my opinion, the largest hurdle player control has been needing to get over. For real, ignoring the comfort/ergonomics argument, focusing just on the movement aspect, the left analogue stick of a traditional controller is better than WASD for movement because it allows variable directions and pressure, but the mouse has the right analogue stick beat for looking because it's far more accurate and acts as a pointer where speed can be easily changed and managed on the fly. I find that accurate looking is far more important than accurate movement, but that's irrelevant to this point:
For the past 30 years we've been dealing with two imperfect control schemes, both suffering a major blow that the other has already pretty much perfected.
It's weird it's taken this long to have the two working in harmony. Obviously it's primarily a problem of putting a 'mouse' on a gamepad, but I find it weird we haven't even had some kind of PC nunchuck equivalent you hold in your left hand, while using a mouse in your right hand. I've actually tried playing Wolfenstein with an XBOne controller in my left and a mouse in my right and it actually works pretty well. This is, I think, the most exciting thing about the Steam Controller.