Microsoft quietly released two mega-hotfix packs for Windows Vista via Windows Update on August 28.
Microsoft made the two hotfixes -- the reliability/performance pack (KB 938194) and the compatibility and stability pack (KB 938979) -- available to interested parties via the Windows download site on August 7. At that time, the Softies said Microsoft would push the Vista hotfix packs out to customers via Windows Update at an unspecified "later date."
That date ended up being today. Both fix packs went out over Windows Update as "recommended" (not "important") updates.
The Vista Performance and Reliability Pack included a number of fixes, including potential corruption of AVI files, improved performance after resuming from hibernate, and improvements in speed in copyng/moving large files. The Compatibility and Reliability pack adds, among other features, "improved reliability for Internet Explorer when some third party toolbars are installed"; increased printer-driver compatibility and increased reliability and performance of Vista when entering and resuming from sleep mode.
A more complete list of the fixes in the two Vista hotfix packs is here.
Microsoft also released on August 28 a slew of other downloads and fixes for Vista and Windows XP. WinBeta.org has a list of some of the new Windows fixes availablefor download.