I fucking love Four Lions, excellent film. I would say anyone who enjoyed In The Loop should watch this, there's no real crossover of talent but the people in charge of both started off working together and scratch similar comedy shapes.
Four Lions is absolutely incredible. Not only in how hilarious it is, but in the fact that like someone above mentioned, it pulls NO punches. It is a dark, dark film, and one that actually manages to have some actual insight on how suicide bombers aren't inherently evil, just dumb people who are manipulated by those who don't want to kill themselves.