So aside from the lack of PC to Xbox play (given PC can play with PS3 when portal comes out), everything he just said jst showed how out of touch he was, GFWL people can play with Steam, as there has never and never likely to be any segrigation between the two, case in point Fallout 3, which I have on steam and requires both steam and bastard GFWL to launch, (oh how I hate GFWL), besides, until the xbox allows mouse and keyboard support, there would be no point, we saw what happened with shadowrun.
Furthermore, given how MS appears to hate Valve, it's unlikely they're going to allow PC to Xbox play anytime soon, at least as far as Steam is concerned.