Looks like 11/8 is the Vista RTM target -- read the full post for more details.
I've found out that the source of Allchin's concerns was an unexpectedly buggy pre-RTM build of Vista. The previous Friday, Microsoft pushed Vista build 5824 into escrow, hoping that the build could qualify as the final shipping version. But a catastrophic problem with the build destroyed any systems that upgraded from Windows XP, requiring complete reinstallations. After several frantic days of trying to find the bug, Microsoft finally fixed the problem last Friday and reset escrow. On Friday, Microsoft internally released build 5840, which didn't include the bug. Testing over the weekend produced positive feedback.