vista ultimate and quad core

When I started looking into quad core applications, the main problem that I noticed was core usage. Oftentimes, users said that all 4 cores were being used by the program, but some were not being used 100% by the application. I heard that with sp1, vista will be able to support up to 48 cores. But my main concern is that vista 64 ultimate will only use each core partially. Do any of you guys have a quad core system with vista ultimate 64? If so, how is it going for you? Does vista do well when it comes to using quad core to the max, or is it going only halfway?

As PK said: That is a function of the Application, and not the Operating System. As an OS, Vista (XP, whatever) sees all of the CPU cores and can use them as needed. Vista is supposed to be more efficient/aggressive about it than XP, but in and of themselves the OS's simply do not need that much horsepower.

It is up to the application programmers to write multithreaded programs that can take advantage of multi-core CPU's. The OS can't magically force a program to take advantage.