Secondly, could you guys use steamworks instead of GFWL? I like Steam a lot more, as I'm sure many do, and "cloud syncing" of my savegames is very cool, even if I don't use it that often.
Lastly, optimization!
Make your game run faster without sacrificing how it looks:
http://www.ericrisser.com/TrueImposters.html Makes distant objects cost your video card a lot less!
http://graphics.stanford.edu/papers/fragmerging/ "Quad fragment merging" Makes all those fancy "shaders" cost video card less!
I wasn't sure if you guys had seen that second paper, but the thought of a massive reduction in shading costs is very cool. Since it's such a recent paper you guys could be the first ever to implement it in a game!