Well.. most of the games today aren't optimized for quads. They just don't "know" how to use the resources of quad core effectively.
Quads are very good for multitasking, particularly with cpu heavy applications. Some applications are multi core optimized. Folding would be good for a quad.
#4: You can tweak any operating system to achieve maximum performance.
You can stop services exactly like you did in XP (by MSCONFIG)
And you can mange and change visual settings for better performance.