Originally Posted by Rosaline
Steam it must be remembered is actually more than just a shop. I find it's community features vital, and because of those (the ability to chat with friends when in game? Yes please!) I will always have it loaded. Unless games for windows can offer similar, it will not be quite the full competitor (aside from the MS monopoly abuse aspect).
I think GFW Live has all of those things - voice chat, servers, multiplayer matching, achievements etc.