Windows Vista early adopters only: If you've been chomping at the bit to get your Vista PC more stable and efficient, you can get your paws on the release candidate of Service Pack 1, now available to the public for download. This is the release candidate, not the final release, so only brave, impatient testers should apply. Occasional Lifehacker guest poster Brad Isaac says:
I have been testing it today and I think it's worth doing... The benefits I've seen so far are an increase in speed, decrease in CPU cycling and my laptop seems to run cooler.
The SP1 RC is a free download for Vista users from Microsoft; if you install this now you'll still have to install the final release when it drops.