Jason, glad you got to see DRIVE. I can understand feeling emotionally let down by the ending (it's probably better than not caring) because you do want some form of success for Driver, but I think you're right in saying that it's more in tune with his character to end that way. In my post on DRIVE (it's titled "The Good Shark" if anyone is having trouble finding it from September), I talked about how Driver is absolutely a killer (and not a killer with heart of gold), but a killer, like Dexter, with a code of conduct to live by–the code of cinema. I think Driver likes playing the role of the cool, composed male protagonist, and he just carries it out the way he thinks he's supposed to from what movies have taught him. The ending is either his way of living out an ultimate martyr film fantasy or protecting Irene from his vicious side (might be both). Either way, I like how Refn lets us know that Driver is doomed the moment he decides to go into the restaurant (Live by the sword, die by the sword) with the flash forward cuts to the stabbing and the shadows looming large instead of the images themselves. It's quite anticlimactic in it's displacement from the real event, which I think is Refn further telling us that this is the only way Driver's tale can end. Anyway, I liked the ending quite a bit.
I'm glad you mentioned the atmosphere of the film too because I think this is one of its real strengths. It feels incredible, and that's one thing that shouldn't be neglected when talking about the film. I think some people are afraid to admit the aesthetic feel a film can have tonally or sonically because it doesn't have anything to do with intellectualizing. It's the same way with literature. Everyone is looking to deconstruct a novel and refill it with theories on writing so much so that they can no longer express how literature feels, how words sound, and how purely beautiful writing can be. I think DRIVE mixes music and silence and image together to create a rich texture of sensuality, physical longing, and brutality. It puts you in the mood, let's say, the way Tarantino or Leone can or the way A SINGLE MAN and IN THE MOOD FOR LOVE do. You feel something, if only because of the way a piece of music matches to an image and seems to seep through its very fibers and then reach out and seep into yours.
I really gotta see DRIVE again. And I gotta get an awesome scorpion jacket so I can have a showdown with Ben at Margarita's. If DRIVE has taught me one thing, it's that you gotta live and die by the code of the movies.