According to CRN, on SP1's kill list are products from Trend Micro, Zonelabs, BitDefender, and Novell.
Some of the companies have come up with work around for Vista's SP1. Some just no longer work.
This site has a list of other problems with Vista's SP1 according to the computer support staff at the University of Pennsylvania.
The Ivy League school's technical support staffers advised "continuing to use previous versions of Windows XP and Windows Vista until after the initial bugs in SP1 are identified and fixed."
Maybe we need to wait on installing Vista's SP1 for a little while.