Aronofsky has a great style and is really effective at conveying paranoia, fear, etc.... His stuff reminds me a lot of early Frankenheimer ( particularly Seconds with Rock Hudson, of all people)....if Frankenheimer had been raised on MTV. I can't wait to see what he does with the next Batman film.
I liked Requiem a lot, but I thought Pi was better for being a less predictable movie. Of course, drug movies don't have a whole lot of choices. Things will inevitably get worse...and boy, do they get bad in Requiem. A small criticism, however, and I will gladly spend $10-$20 on this or any other DVD that will make it easier for producers to continue to put real dollars in the hands of great directors like Arnovsky, Chris Nolan, the Coens, the Hughes', David Fincher, David Lynch, Paul Thomas Anderson, Spike Jonze, Lars Von Trier, Julian Schnabel, Mike Leigh, Todd Solondz, Mike Figgis, Atom Egoyan...the list goes on and on.
By the way, if you liked Pi, check out Shinya Tsukamoto's awesome low-budged freak show Tetsuo.