When an almost 3 hour film goes by so quickly that you don't have to check your watch once you know it's good.
That's my philosophy too.
I saw Les MisÚrables the day before Django Unchained. With Les Mis I was checking my watch every few minutes, with Django I couldn't believe it was over so fast.
Great to see it get a couple of BAFTAs - Christoph Waltz was superb.