My experience..
.. was that service pack 1 did appear to have a beneficial effect. It stopped the PC crashing every 5 minutes, but many many many bugs still remain.
However, last night windows update informed me that there were updates for the X64 version. How foolish of me to install them!
Now "Windows Media Centre" refuses to play back it's own recordings smoothly, the computer will no longer go to sleep (so ofcourse, can no longer wake up to record TV), applications that worked flawlessly now bomb out with either a BSOD or the "Check for Solution" dialogue (which then crashes).
Even after SP1 Vista is still very much a beta, no one in their right minds could use it for anything that needs reliability.