I'm still very early into the script, but the first thing I've noticed is how there is a strong set piece early in the film.
Three men chained together, Everett gets onto the train but instead of helping the others get on he instead opens a verbose conversation with some hobos. Behind him the last convict falls and the other two are dragged off.
The important thing about this set piece is it tells the audience that they can relax; this film is going to be funny; it's been made by people who know how to set up a classic gag.
It's got great comic elements - a pompous man is made foolish by his own pomposity. It also conforms to the comic rule of three. One is the set up, two is the build up, three is the punchline. It works everytime.
The other thing I'm enjoying is how sparse the script is. It's obvious that the writers intended to direct, this script isn't driven by a need to sell.