In Windows 7 the User Mode Scheduler provides a new model for high-performance applications to control the execution of threads by allowing applications to schedule, throttle and control the overhead due to blocking system calls. In other words, applications can switch user threads completely in user mode without going through the kernel level scheduler. This frees up the kernel thread scheduler from having to block unnecessarily, which is a very good thing as we move into the age of Many-Core.
THe best way to make use of this new feature is ConcRT. "ConcRT is built on top of UMS and is the best way to most effectively utilize this new user mode thread scheduling model in Windows 7 (download)."
Demo: Video (WMV)