I love Barton Fink. It's probably my favorite Coen film after the Big Lebowski, although I love them all.
John Goodman running down the fiery hallway is one of the coolest moments in movie history, and both Steve Buscemi's and Tony Shalhoub's cameos are hilarious.
I think the pivotal moment it when he finds out that W.P. Mayhew is a drunk and that his secretary writes his books. When he realizes that, the whole facade of Hollywood falls down for him (just like the wallpaper) and the gentle working man next door is exposed as a psychopathic killer.
Also, the film seems to be about "heads." The decapitations, the head in the box, "where there's a head, there's a way", "the contents of your head belong to Capital Pictures," etc. There are some I'm forgetting. The mosquito, the girl on the beach, and the bird falling into the water are just the Coen's not taking anything seriously a usual, I think.
Anyway, I can't wait for this on DVD.