Bornakk just posted that the downtime has been extended until 1:00 p.m. PST / 4:00 p.m. EST. This is never a good thing when maintenance gets extended, but at least Blizzard is hard at work on the servers.
We haven't received any information that there are any new hotfixes being applied. So we'll probably have to wait to log in to see if any of the bugged quests are fixed or not.
WoW Insider will update you when the realms are up... a few hours from now.