But that's essentially all we can use to judge whether we will want to see the movie or not.
I mean if a movie trailer is really good in my opinion, or catches my attention, or whatever, then I will want to see that movie. And then when I actually see the movie it might turn out to be disappointing (Scary Movie 3, I haven't seen 4 yet), or it might be as good as I thought the trailer presented it.
One of the points of a movie trailer is to get the people's attention and give them a crash-course in what the movie is about, before actually seeing the complete product. If we can't use that, what can we use? Remember the title of the thread is "United 93: Will you see it?", not "Did you see it?". It blatantly states that it's a thread of people talking about why they will or won't see it, and one of the criteria for making that decision is the trailer.