"Yeah, awesome, and when steam is integrated to windows, it'll be a great windows service."
Personally I would prefer single integrated DRM platform then having seperate one for every game i play.
Right now there is about dozen of these: games for live, ubisoft game launcher or tages and other bullshits.
Each one updating itself when its wants, changing ur system files as desired, sometimes even loading every time you start your computer using ur memory and cpu power without u knowing about it.
Man if i had one windows service for all my games which i can easily switch off and on why the hell not 
Besides it is not cheap to make game and i mean really not cheap at all. So im glad they only require me to install steam to get fully functioning game.I also belive steam will be in the game to manage multiplayer games and rankings.
Same as I had to have impulse for demigod and battlenet for diablo and starcraft or windows games live for dawn of war and gears of war or ubisoft launcher for settlers and assasins creed or (rotfl) ncsoft launcher for aion and rohan