Windows 7 SP1 leaked -- but you should probably wait for the final version
Apart from the obvious reason that it's a beta release, there's an annoying little problem I've been fighting with on a handful of my customers' systems. It seems that they somehow managed to get their mitts on a pre-release version of SP2 for Windows Vista. One day, out of the blue, Windows suddenly told them Vista was no longer genuine and they had to re-activate.
They punched the license key in multiple times, but no joy. It just wouldn't go.
The solution: remove their SP2 install and replace it with the final one. It's not a complicated fix, but it is one that ties your computer up for a long time and requires several reboots.
I can't say for sure that Windows 7 SP1 will behave the same way, but if you're not a fan of lengthy re-installs you should probably just sit tight and wait for Microsoft to deliver the final service pack. It's not going to be too much longer now anyway, and there's really nothing all that exciting under the hood for the average user at home.