I gave it an 8/10, with 10 being the (IMO, mostly) unattainable perfect movie, 5 being average, and 1 being utter crap. The film was excellently done.
In contrast to some of the critics, I didn't mind the shifting tone towards the end of the movie. (SPOILERS)
[sblock]I think the idea was to convey the feeling that over the course of 74 hours, things started at very simple and spiraled wildly out of control. In the beginning, you could take a break and think. However, everything quickly became hectic and there wasn't time to think, just to act.[/sblock]