WordPress MU version 2.7 was released today. I’ll be doing the upgrade in the morning on Friday, Feb 6. You will notice a significant change in the back end interface, which was redesigned to be more user-friendly in version 2.7.
I don’t expect more than a few minutes downtime, but this is the first time doing a WPMU upgrade, so it may be a bit longer. In the case of major problems, if the upgrade isn’t complete by 11:30 am, I will revert and restore from backups.