If you don't see it in Windows Update, then you may have to install all optional Driver updates. There's a very small conflict with certain drivers (more details at Paul's Windows SuperSite). SP1 for now is an opt-in update. However, it will be pushed by Automatic Updates next month. However, the SP1 installer will always require your consent.
After installing it last night, my laptop didn't freeze up on me after 10-15 minutes and requiring 1-2 reboots as a result like it has been the last few weeks (the last couple updates to Vista had to be the cause as it worked fine until then), so hopefully SP1 fixed that problem.