Microsoft was forced to delay the release of the final version of Windows Vista to manufacturers due to a bug found in the final stretch of testing. IDG News quotes a tester who revealed that the bug “would totally crash the system, requiring a complete reinstall.”
This bug has been taken care of, but has delayed the RTM process. There are 499 known bugs that still linger, that will not likely be fixed prior to the RTM. I think it’s safe to say that Windows Update will be the first thing you will want to run once you get online with the new OS.