If Valve makes it possible to game versus PC-gamers through this box it will be even better than the other consoles.
People could complain about players having (dis-)advantages but then again you could say that about people using a simple mouse/keyboard combination when facing somebody using exceptionally good mouse/keyboard. My brother for example played BF3 on PC and Xbox 360 and was way better on the Xbox version so I'm pretty sure it comes down to preference.