I got to see this at a local AMC today. As far as I know, it's definitely the first Korean zombie movie I've ever seen... and perhaps it's because of that novelty that all the well worn zombie movie tropes felt fresh to me.
OR... it's also because TRAIN TO BUSAN is an incredibly well executed genre movie!
The zombies in this are of the Snydawn of the Dead/World War Z type. They're super-ragey and climb over each other to build structures of their bodies. They turn fast and contort their body in fun ways.
It's also a bit THE HOST as well as SNOWPIERCER (not just because of trains and Korea, but also because of the blatant class/morality commentary peppered through the film).
There's really not much more I can say about the film that wouldn't be redundant (it is very true to zombie movie tropes) or wouldn't reveal the film's smaller surprises and pleasures. I really enjoyed the supporting cast and found the filmmaking to be smart and very effective. It escalates the situations really well and always manages to avoid becoming too repetitive... at least until the end when it really stretches out the finale for one climax after another that eventually leads to a super melodramatic finale (it is a Korean movie, after all).
I was really pleased with this. If you find it playing anywhere near you, I'd highly recommend it.