Shacknews posted an article about some of the things that were announced at Microsoft's Gamefest 2006:
Though many of the technical and marketing issues related to the platform as a whole will be tackled by Microsoft, Windows is still an open development platform and so it is a bit trickier to fully standardize actual game features. To encourage developers to take advantage of Vista-specific features and make their games compliant with the overall Games for Windows initiative, there will be a set of recommended and strongly recommended features called Showcases and Essentials.
Essentials are checklist features that Microsoft will stringently require for developers who want to take advantage of the marketing support being placed behind Games for Windows. Again, there is no way to actually require a feature in Windows games since the nature of PC development means there is no mandatory licensing program, but only developers that adhere to the Essentials will get the substantial marketing muscle being placed behind the platform. Assuming the support Microsoft gives to Games for Windows is attractive and effective enough to entice developers to want to participate, the overall accessibility and compatibility of Windows games should theoretically increase as those developers implement Essentials.