Damn, just damn. That looks incredible. You really get the sense of how personal the story is for Tony Stark and some of the imagery in the trailer (Stark's home being destroyed, the old Iron Man suits being blown up, Stark trapped underwater beneath the wreckage of his home) is brilliant. Have to give praise for the casting of Ben Kingsley as the villain, The Mandarin as (although he isn't what is expected from the character), Kingsley is great at playing villains and it'll be great to see how he fits into the Marvel Cinematic Universe.
Overall I'm really excited for this, the franchise looks to be in good hands with Shane Black (BTW if you haven't seen his previous film with Robert Downey Jr - Kiss, Kiss, Bang, Bang - go and see it to see how brilliant his dialogue can be) and I will be watching the film as soon as I can when it comes out.