Microsoft has quietly released a RC build of Vista SP1 to the public.  You can get it here: http://technet.microsoft.com/en-us/windowsvista/bb738089.aspx  I installed it and did notice a small performance increase overall, but boot time seems longer.  I had a “Crash” a few days later where my screen was black and only the cursor was shown.  I had to reboot to clear the problem, but other than that it seems an improvement.  Again, I suggest waiting for the official release.  Note that according to the readme you will have to uninstall this RC1 before installing the final release.  The install took about an hour(!) to complete.   One of the benefits is that if you have a system that is not activated, it will allow you to continue to use the OS, but will nag all the time instead of putting you into a reduced access mode.