This will be my first comment about a film that I've not seen which, merely, puts me in the company of the other commentators.
I was curious about what sort of person (if any) might actually sit through such a movie. I'm sure Andy Warhol wouldn't. So, when I read the comment that this film was not to be watched, but looked at, I realized the true genius of Andy Warhol.
"Empire" was not made to be watched nor looked at. It was meant to be talked about... And the proof (partially verified here at IMDb) is that we are all reading, writing, and talking about this opus.
I wonder if Andy would have made a followup work "Eiffel Tower" might it be deemed too exciting compared to the tranquil "Empire"?