I only know one case on a B727 where a water leak whiped out the complete electrical system, and that was pretty much in the departure sequence so the aircraft was back on the ground in little time.
In the simulator I have seen many bus failures, for some reason my company loved these during recurrents as for the "pilot side", there are a lot of little unrelated issues to deal with, some more apparent than others. But the result is always a no rush situation...
As for reality: single drive failures, gen failures, I remember somebody had a battery bus failure in the UK with some smoke?
So a full and non-recoverable loss of all AC power generation is really lottery level stuff.