There's nothing new under the sun when it comes to post-apocalyptic fare these days; the market has become a bit oversaturated. With that said, having a train as a basis for society's levels is an intriguing concept and that's actually one of the movie's strong points. Bong has a keen eye for visuals, and although he sacrifices sense for style at times, he makes it well worth it. There are some really pleasing shots in here, and the range of warmth and colors throughout the train is probably one of the best parts of this film. Each new carriage is like a new level in a video game, with creative surprises for our intrepid protagonist and his band of (not so merry) men. Even though the camera action and story is strictly linear, never does Bong seem limited by the lack of space or direction. The movie does lag a bit in the beginning, but once it picks up, it carries the momentum straight to the end (or as it were, the front of the train).
The Host, which was Bong's smash hit, combined a love for monster horror flicks, and a knack for navigating the political weaving that really is the backddrop for that genre. Snowpiercer is no different in playing with political satire, raising the question of the disparity between levels of society and why that is...and who enforces it. It's a bleak look at human nature, and you have to appreciate the script for being unsparing. Some moments are humorous on the surface until you realize how close to home it might hit...but the film is not without some hope in the message.
Of course, having a stellar cast never hurts. You can never go wrong with Tilda Swinton and it's refreshing to see Chris Evans in a role outside of the perfectly coifed boy scout Captain America. Jaime Bell and Bong regular Kang-Ho Song are great at what they do, as usual. A pleasant surprise is Ko A-Song, who has grown up since her role in The Host and whose grasp of the English language doesn't obstruct her acting (which we've unfortunately seen in the past...Sorry Gianna Jun and Donna Bae. Close but no cigar).
On a last, unrelated note, I think my rating system has gotten more and more arbitrary.