Lack of good storyline.

It's fun, it's light, [but] it has a hard time when its tries to get heavy.

Yes, absolutely, there is fun to be had, as well as many, many things to go boom, all amid an atmospheric urban jungle.

Very good movie overall, highly recommended. Most of the negative reviews don't have any merit and are all pollitically based. Give this movie a chance at least, and it might give you a different perspective.