Around 5 hours 1 minute to beat, with Ending A. For this ending you choose to join the mayor after beating the first 4 missions. I plan to go for completing all 5 missions, after unlocking some more characters. Really enjoyed this game, despite some bullshit. Once I complete all 5 stages I may post a tutorial on the game. I will definately review it.
Machine Gun Willy is a great unlockable character. Slow but can really line up groups and wipe them out. Whenever you kill 3 people at once you get a food pick up, so this is a good way to stay alive.
I went with this specific route as I did not want to deal with Machine Gun Willy as the 4th boss this time. Last time I did that he stayed in the helicopter while summoning minions, and was very hard to damage. Depending on the order you choose stages, the later stages are longer and the bosses change to become more difficult. They can be completely different boss fights as well. I will go into more detail if I ever make a tutorial.