For plenty of people, a big reason to upgrade to Windows Vista SP1 will be the death of the dreaded "Kill Switch," which in essence kills Windows if for some reason Microsoft determines your copy isn't a validly bought version. Good move...but getting rid of the Kill Switch is something that Microsoft can easily do as an update without bundling into SP1. So why hold it hostage until SP1 ships? To force you to upgrade, and make the service pack's uptake numbers look better.
First, a bit of background. The Kill Switch built into SP1 goes into effect if you don't activate a retail version of Vista after 30 days, or if you ignore a three-day grace period you're given after making so many hardware changes that Windows is no longer considered valid. Your desktop turns black, the Start menu and desktop icons disappear, and you can only copy your data files, but you can't open them. In addition, after you use Internet Explorer for an hour, you're logged off.
With SP1, the Kill Switch will become a nudge switch. As Computerworld has reported, you'll still be able to use Windows, but you'll get reminders to validate it, your desktop background will turn black, but the icons and Start menu will remain. You can still use your PC.
Microsoft, Windows Vista, Service Pack, SP1, Vista SP1, Kill Switch, WGA, Windows Genuine Advantage