Bit Tech has talking to the guys at Bethesda, developers of Elder Scrolls: Oblivion, about their development work on the Xbox 360 and PC. There's some great info in there, including the problems of working with a unified graphics architecture and the advantages of working with multi-threaded architecture.
"Oblivion will absolutely benefit from a multi-processor or multi-core PC architecture. These improvements have largely been driven by our optimizations for the Xbox 360 hardware. We have built a dynamic thread management system that manages processor load by our specific direction and by priorities. Portions of physics, AI, loading, audio, and rendering tasks can all be moved to different threads to keep the overall load balanced. The net result for the end user is a smoother experience."