Thor vs Hulk ends in a stalemate. The fight begins on the helicarrier after Banner hulks out and almost kills Black Widow. A huge fight between the two ensues (they're about even in terms of power levels) but eventually ends when Hulk is distracted by a SHIELD fighter jet.
Stark Tower becomes The Avengers Mansion. It's damaged during the battle for NYC but an A symbol can be seen on it at the very end (in a scene involving Pepper and Tony).
The events of The Incredible Hulk are acknowledged as in continuity. Tony watches a clip of the Hulk roaring from the park scene in TIH, Coulson briefs Captain America on the variation to the serum Erskine made (i.e. what Blonsky had), and Ruffalo's Banner talks about how he leveled Brooklyn (i.e. when he duked it out with Abomination).
Thor flies only a handful of times during the film (once or twice in the battle at the end).
Pepper Potts is implied to be pregnant.
The battle in New York City lasts between 15 and 20 minutes.
The Leviathan(s) is not named in the film, and there are in fact
three of them.
Agent Coulson is killed by Loki. He tries to use a gun created from the technology of the Destroyer armor on him (in order to save Thor), but gets stabbed. He does manage to fire the gun as he dies.
Thanos is the villain in the mid-credits scene (CGI, but possibly voiced by Jeffrey Wright). One of his minions remarks that to interfere with earth would be to "court death", at which he smiles.
Asgard and Odin do not feature in the movie.
At the end Thor leaves Earth with Loki and the Cosmic Cube.