Microsoft is shutting down both the GFWL & Zune Maketplaces. Both are slated to get the axe on 8/22.
If you have PC games that you have not yet bought the DLC for, you may want to do so now. You will still be able to play the games, and download disc versions. You will no longer be able to download digital versions, not even as a redownload from tour history. Also, apparently Steam is going to release updates that removes the GFWL component from titles purchased through them, as they did with Gotham City Impostors.