I checked this movie out today. Despite the fact that I knew (more or less) exactly what was going to happen, the director did a good job of keeping me on the edge of my seat. I don't really know if entertainment was his intention, considering the subject matter of the film and its broader purpose, but the movie served to entertain nonetheless. There also seemed to be a small handful of political undertones regarding the handling of the emergency. Nothing too blatant though.
I've always felt somewhat bad or shameful because I've never been as emotional about 9/11 as seemingly everybody else. I wasn't even all that shaken up the day of the event (I woke up after noon, at which point my roommate quickly recapped me on what happened). I was more surprised than anything else. It's made me feel somewhat cold hearted. However, this movie REALLY tugged at my heart strings throughout, and most movies don't do that to me.
I should note, however, that a lot of the acting was super cheesy and bordered on awful. I think the actors that played the hijackers all did a really good job, as did most of the passengers and crew members. A lot of the family members on the ground (who were speaking to the passengers via cell phones) were pretty bad, though. I'm talking high school play bad.