might wanna approach impulse too as thats a little like steam!
Already done http://impulsedriven.com/dof
And while I agree with above posts about Steam - their community is growing every day - and lets face it - they are the biggest online retailer of PC games. Although I heard rumors Windows 8 might screw up their business model. But either way - few more days till Greenlight goes live, can`t wait to get DoF up there!