Confirming reports that arose yesterday, Microsoft has made its first service pack for Windows Vista publicly available. The pack can be found on Windows Update right now, and folks can download it from Microsoft's download center in both 32-bit and 64-bit flavors. The 32-bit version is a 434.5MB download, while the 64-bit version is a heftier 726.5MB. However, Microsoft recommends that end users get the service pack through Windows Update, which it says will cut the download size to "about 65MB."
A detailed list of the changes and fixes introduced in SP1 can be viewed on this page. Notable changes include the addition of support for DirectX 10.1, the Extensible Firmware Interface, and the exFAT flash storage format; greater reliability, namely in applications like the Windows Calendar, Windows Media Player, and bundled drivers; performance improvements with tasks like file copies and file deletions, SuperFetch, and ReadyBoost; lower power utilization; and general enhancements like a reduced frequency of User Access Control prompts in some instances.
A word of warning, though. Some device drivers cause problems with SP1, which is widely said to be the reason Microsoft postponed the service pack's release last month. According to Microsoft, users with problematic drivers won't be offered the update through Windows Update, and neither will those running versions of Vista that aren't in English, French, Spanish, German, or Japanese (releases in other languages aren't available yet). SP1 will only be pushed through Automatic Updates in the middle of next month, as well.