My twopenny's worth:
I'd feel happier flying an aircraft being rested and having consumed one beer than flying when severely fatigued. I base this statement on my driving performance after operating on a 10 hour two crew return flight from Florida having taken off at midnight body time with irregular and disturbed rest. Please bear in mind I had just recently landed the aircraft!
Also, I heard a fellow pilot once comment "If our pilots made as many errors our management makes, there would be aircraft wrecks all over Southern England".