I just installed SP1 through windows update last night and everything went quickly and flawlessly. I noticed an immediate performance improvement even though the superfetch cache had been cleared so I can only imagine that it will get better over the next few weeks. Overall, everything just seemed to respond a little faster and little more smoothly. Hopefully I won't be eating my words anytime soon.
For those who are curious, my Vista machine has this setup:
Vista Home Premium 32 bit
ASUS M2N32-SLI Deluxe Mobo
The standard SoundMax onboard for that mobo
AMD Athlon 64 X2 series CPU
Nvidia 7800GT 256mb
2GB Corsair memory (I forgot the details, but I got it a year ago and it was supposed to be some of the best quality RAM they had at the time.)
So far I have had no driver issues or software mishaps at all. I am able to play video just fine, games work great, and I am having no internet or networking issues. I was nervous at first because of the rumors I was hearing about Nvidia driver issues but I have not had a problem yet. I do not have a DX10 card though so I am not sure if some of the video issues I have been hearing about are isolated to that. The only thing which I have not tested yet is whether or not my setup with the 360 is still working fine for wirelessly streaming videos and music through WMP11. I'll test that today.