Location: Los Angeles, CA
I heard that Aronofsky shot "Pi" on 16mm tri-ex REVERSAL film stock, which means there's no negative -- you're stuck with that one copy of the film, so if it scratches or tears, you're screwed. But the grainy look of that reversal stock looks better than the negative stock, thus the film looks great.
Let's hope more filmmakers listen to Nolan's call to use film, not digital. And not just the big Hollywood filmmakers, but indie directors, too.