Like Darren I've updated from to build 5472 of Windows Vista and I've also updated to the "Tech Refresh" build of office 2007. These interim builds can be "two steps forward, one step back" - 5456 was faster than the Beta 2 build (5384) but some things that had worked before were broken.
5472 is showing more speed still, some little improvements in fit and finish (polish to Icons, new screen saver, some wrong fonts fixed. The implementation of Info-cards has become Windows CardSpace , Windows Collaboration is now Windows Meeting Space ). And some of the things that broke between 5384 and 5456 are working again.
Working, then Broken then Fixed,
On that last point try the following to see if you're affected. Start the Resource Monitor - either from the performance tab in Task manager, or from Reliability and Performance Console on the Start Menu. You should see something like this.
I think that in "Balanced" power plan the Maximum frequency for the CPU is never 100% - but that it should be when running on mains power. I haven't found a way to persuade this power plan to give me full CPU speed, so I've changed to High Performance.