Well i have always said that blue screen is caused by hardware and Vista SP1 shows this again. I have applied SP1 to 3 Machines a dell Latitude D620 and a Motion Computing LS800, and a home made PC that about 2 years old.
On the Motion and the Home made PC. I had Blue screens of death during the install. It was kind of ugly the Motion took 21 hours to finally finish. That was after 2 attempts. But after researching both Blue Screens I found that I had a Bad SD card reader in the Motion Tablet. (not sure it is bad but it never has worked) I had forgot about it.
And on the home computer I had an old hard drive that I have never removed it was just disabled. SP1 Reenabled it and of course it failed badly. once I removed the hard drive and disabled the card reader all seems really good.
Overall not a bad install if you think about the fact that in all cases I could get to the things I needed to to fix the problem. So not bad but you need to make sure your hardware is good if it is not you will have a few issues.