I think the purpose of this trailer is to sort of wash away the old feelings of the prior Batman movies in the public eye. When you say Batman to most people, they think of bright colors, rubber nipples, and all-and-all out stupidty. This trailer isn't so much to entice people to come see the movie, I think, as it is to introduce people to the fact that there is a new Batman movie and that it won't be like the others. Sort of a "Hey... you know those other Batman movies? Well, this new one is different" kind of deal. I'm sure the real trailer will be the "Okay, now that's out of the way, here's ass-kicking."
I for one enjoyed it. Confirmed the direction the franchise is going, that the style of the film is being heavily controled by Nolan, and that this will be a much darker, more personal film than probably any of the movies currently swirling in the comic book crazy market right now. As of now, the darkest super hero movie out there in the recent comic book swarm is probably Daredevil, whereas the Hulk is probably trying to be the more artistic and X-Men being the most balanced of that. I think Batman is going to come in and bring some very needed darkness and maturity to this kid/teenager friendly market. Note: I love the Spider-Man and X-Men movies, but I think if Batman Begins doesn't have Bruce in the cape until half-way through, excellent. That means character development, and character development is a good thing.