Full of mixed feelings after watching this movie. I say this because I simply loved Joon-ho Bong's direction, he was really capable putting all the brutality typical from a South Korean movie into a Hollywood one, and I say this as a huge fan of his most famous work, Memories of Murder.
But the plot, well, the concept of a train being the last stand of humanity is just... dumb. Ok, I can get all the metaphorical implications here, but from time to time I couldn't stop myself getting my mind out of the screen to think "well, this doesn't make much sense".
About the ending? I liked it, it fits really well with the thematic of the whole movie, but than again, it just confirms how dumb is the idea to put the whole humanity inside a train.