I heard it was pretty good. I also heard from another person that it wasn't good as the first two, but still pretty good in its own right. I wasn't looking too forward to seeing it as I'm a huge pussy and I haven't seen the second one, but after hearing about how good it is it makes me want to watch it.
Viral Video compilation: http://www.youtube.com/watch?v=GPPWnb-YZik
By the way, if you're the kind of person that feels that trailers spoil parts of the movie, don't worry! Nothing in these trailers, as far as I've heard, is in the actual movie.
Alright, talk away!