The PC version of Colin McRae: Dirt 2 is being driven to December in order to make sure the title supports the hardware tessellation, multi-threading and Shader Model 5.0 technology coming in DirectX 11.
DirectX 11 already? Most games are still trying to catch up to DirectX 10 support, but Codemasters wants to make sure they deliver the "most realistic, immersive and exhilarating racing experiences in the business", and that means the Games for Windows Live version of Dirt 2 is just going to have to wait a few months. With the console versions still on target for a September release, PC users will have to wait until December before they get a much nicer version of the title, provided they have the hardware to support it, of course.
Why not simply release the game and patch in DX11 support later? Perhaps Codemasters is taking a cue from the previous generation, where PC developers' promised Direct X 10 patches trickled out far later than originally planned, impressing less people in the process.