The servers did eventually come back up around 1am EST this morning, but there was still missing in-game mail and there were many other problems with PVP gear venders that apparently necessitated another round of maintenance this morning. The servers went back down for an advertised 3 hour maintenance at 7am EST and are still down. While I understand sometimes things happen, they seem to be happening with some regularity lately. And that isn't making me very happy. I've been trying to complete my Netherwing grind before the expansion hits and I lost an entire day of rep yesterday. I was working on it again this morning when I got up only to find out the servers were going down again. I'm not entirely certain this bodes well for tonight's expansion launch.
10:35 Update - the servers are still offline. Blizzard posted a new note indicating they ran into unspecified "database issues" and no new ETR.