As revealed the other week, and now actually actual - right over here. There's not a vast amount of super-recent games on there as yet, but Lego Universe, Dead Rising 2 and 007: Blood Stone are the headliners and suggest a drive to be relatively contemporary. A lot of the existing stuff remains comically expensive, however, which suggests that publishers are either very cautious about this service or Microsoft are still testing the waters. Clue: be cheaper.
There's an inaugural mega-bargain, at least - GTA IV, sans DLC, for £12. Alas, it has been cheaper on Steam during past ultro-sales and can still be had for less at retail/etail, but if the high street or a wait for the post-person ain't handy for you it's certainly cheaper than any other digi-store right this minute. You can also use your Live/Messenger/Hotmail/whatevs id to sign in and buy stuff, which might make it a little easier or more palatable for some folks. Or not. WHO KNOWS?
The roster isn't, it must be said, especially impressive right now, primarily consisting of stuff that was on the old version of the service, with the addition of a few older Activisoin titles. The two most recent CODs - both requiring Steam - are noticeable by their absence, so I'm not terribly convinced anyone's gonna rush to pick up World of War right now... Still, it means it genuinely is hosting games free from Games For Windows Live.
Then again the service has just relaunched, so it's unfair to sneer before its wheels have fully begun to turn. I entirely appreciate that it's going to take a little while to fill up with the promised wave of Live-less titles. In general, the predominantly web-only interface seems admirably de-cluttered and de-cludged compared to previous incarnations of GFW Marketplace, but forcing people into having a Live account might create some annoyance. Give it a whirl, anyway - seem more appealing than a) before b) other services c) shops?
Update - as Miker cleverly suggests below, GFW also allows (but doesn't force) you to pay in MS points. And there are quite often offers to buy MS Points discounted, if you keep your ear to the ground, so it's entirely possible that canny PC gamers could snag bonus price cuts. A potentially effective spanner in the (Steam)works, if the new GFW pulls in enough desirable games over time.