ASICMINER just turned back on at BTC Guild [shares counter started increasing again, and speed did not fully drop to 0]. Remember that the speed shown on hall of fame is a 1-hour average, so don't be alarmed if it looks like a slow growth back up.
Seems to be hovering around 2TH, so I am assuming not all miners went back online....
Sorry I didn't post this last night: I was told that the speed will not be stable today, so don't spend too much time spamming F5 on the rankings page. They are aware and expecting to see fluctuations in speed throughout the day as they work.