I didn't know what to expect either.
I kept wondering about the black/white tape at the beginning, wondering if some kind of crime would happen. Just before the show the title of the movie they go back and show the whole picture, then I finally see the date beside the time. Then I realize what it would be about.
Still my imagination was not as "real" as the movie would be.
It is not about the characters, it is about people. How the firefighter captain speaks the words that are in his heart, the author just types into a machine. Words that catch the people as easily as the events had. Good words can ease the suffering. Nobody will ever forget the day Rambo, Superman, Batmann, yet the whole League of Justice, Wonderman and all the other superheros were on a sponsored company pick nick and here many people died. It was a reality check for everybody.
Although I like Bill Murray, who did the theatric play with SW, I think Anthony LaPaglia did a good job. Maybe he got the role because he is starring in the TV show Without a trace which is about missing persons.
I never doubted Signourney Weaver.
Don't watch the movie totally unaware what will happen. The events will overwhelm you and when you think you made it through the movie without crying, wait for the end. Watch it and remember where you were and how you felt. And remember the people you love and tell them.