Together with the final release of the first service pack for Office 2007, Microsoft has made public a release candidate of its first Windows Vista service pack. The Vista SP1 RC is freely available to download as part of Microsoft's public availability program. The installer only weighs in at 348KB, but it presumably fetches a good deal more data as it's applied.
Among SP1's updates are search changes (in order to accommodate third-party desktop search software), and modifications to the Windows Genuine Advantage software that no longer locks Vista in a "reduced functionality" mode if it deems the operating system to be a non-genuine copy. There's also a new feature called hotpatching, which allows Windows components to be updated without requiring a reboot. Finally, users can expect performance improvements. A report on Gizmodo suggests that Vista SP1 significantly increases network speeds compared to the "release to manufacturing" version of the same OS.
Beware, though. This SP1 release candidate is intended for testing. Microsoft warns that it won't provide support for it, and the company's release notes mention some outstanding flaws. Folks who'd rather not deal with the eventual possibility of having to reinstall their operating system probably ought to wait for the final SP1 release next quarter. Others should take care to follow the instructions on Microsoft's download page.