Very, very fast. It seems quite a bit faster than any of the RC1 builds. They've fixed the 8237 SATA driver so my sound and mouse no longer skip during disk activity. It still is not perfect since firing up Media Center for the first time caused some skipping and popping of Pandora playback but it cleared up quickly and so far has not returned.
Install was a bit unstable. It blue screened during install giving some error related to "Drive Power State". I had upgraded the firmware on my LiteOn DVD-RW drive just the day before so it might have something to do with that. The install wasn't trashed however. I just restarted the machine and it restarted the install stage it was in. No sweat.
So far, all my apps are working flawlessly and are just flying. Aero seems a bit faster than with 5600 or 5728 but is still sluggish for me as my Experience Index is 2.0 caused mainly by my aging video card.
It's clear that this build includes quite a few optimizations that did not exist in previous builds. I question the wisdom in introducing the optimizations in what is said to be the last public release before RTM but it's clear that Vista is shaping up to be a fine replacement for XP. It's true that Microsoft ripped out alot of the cornerstone features of Vista but what they left is a good foundation for followup work.