From David Chatham:
As of 6:30 a.m. the estimate is that the Vista upgrade will take another four or five hours. The upgrade is progressing with few errors so far. When there is an error, the engineer has to stop the upgrade and fix the error then start it again. So far, he hasn't seen any errors, but they underestimated the time to process this size installation.
One other thing I need to mention. If the upgrade bombs and they get a fatal error, then they have to abandon the upgrade and restore to the original instance. This could take eight hours. Originally, I was given an estimate of 8 hours, including a potential roll-back if necessary. I am keeping my proverbial fingers crossed that we don't have that rare situation.
I plan to monitor this and will provide an update when I have one or when the process is done.