It's about time! If you've copied files and wondered why it was taking Vista so long to do a simple task, here's the update for you.
KB 938979 "performance and reliability" update addresses (among other things) the "file transfer" problem, which Microsoft describes as, "When you copy or move a large file, the 'estimated time remaining' takes a long time to be calculated and displayed." This is what I referred to my coworkers as the "why does it take so long to copy one file?" problem.
KB 938194 "compatibility and reliability" update deals with some video card issues and a printer problem, so you may want this if you 1) play games on Vista or 2) have a problem with print spooler dying unexpectedly (although I'm not sure it will fix bad drivers).