I downloaded it last night, and installed it just a few minutes ago. The install process was surprisingly short and painless, the machine booting to how I remember it before running the update.
Something I always do before running any major service pack is turn off anti-virus protection. WinPatrol has a facility to disable/enable start-ups very easily, just one more reason for having it installed.
Well, so far so good. If I get any problems, I will post them here..