Microsoft have launched Games For Windows Live Marketplace for the PC. This is basically their version of Steam where you can use your Windows Live credentials to log in and buy games. They already have 80 plus PC games ready to be downloaded, with more on the way.
Like Steam they also offer demo downloads and daily deals, although I can’t see too many people warming to this new system unless they’re Xbox folk and are new to PC games. There’s really no benefit that I can see to having this running on your PC along with Steam. Steam is pretty stable these days, after years or refining and offers great deals on PC games week in week out. Microsoft have a mountain to climb if they are thinking of enticing Steam users over.