This has instantly become one of the my favorite movies.
The first scene of the movie, the actual 3 or 4 day, up all day and night partying scene, I was thinking, "Hasn't there been enough movies made about people that just do drugs all day? Trainspotting? Requiem for a Dream? Isn't that enough? Why must there be another?"
Then the movie just goes in a completely different direction and becomes a great character study of Danny Parker / Tom Van Allen. This has passed Wonderland, The Doors, Heat and Kiss Kiss, Bang Bang as my favorite Kilmer performance.