The series is (in my opinion) much much better.
I'm 5 episodes in and it certainly does draw out the main premise in significant detail. You're right, its a good show -- there's a lot more at stake than with the movie as there is all this advanced plot and character development going on. I think the train is much bigger and longer than in the movie, which is cool but hard to fathom a train being a few miles long.
The train is 1001 wagon long,
It also has 2 levels (sometimes 3).
One level where people live and one technical level below with all the machinery and stuff.
I have finished the show, what a great ending.
Definitely better than the movie.