Went and caught "United 93" this afternoon. Very well made. The majority of the film is 9/11 from the view point of air traffic control which I thought was interesting. The first hour is them edited with United 93 boarding, waiting on the runway, etc.
The film only contains events that we know happened on the plane based on phone calls and such.
For the first hour, I had an uneasy feeling in my stomach. Just the suspense building up from what inevitably was going to happen.
I agree with all the critics in that it is well done, does not exploit anything, and is a movie, if you can handle it, should be seen.