The film was very well balanced between all of them. Every avenger had their moments to really shine, even Hawkeye and Black Widow. Favourite moments were Thor holding his hand out for Mjolnir and then smashing Hulk in the head with it, Hawkeye jumping off the building and firing, Iron Man bouncing his repulsor beam thingies off of Cap's shield, Captain America beating up a bunch of Chitauri and then the cut to the cop issuing the orders he had just been given, Banner transforming into the Hulk for the second time, Thor and Loki talking on the cliff, Cap saying "hulk... smash", and I could go on but really need to see the movie again and soon..
In terms of how they dealt with Thor, I felt it was similar to the Hulk. He's very powerful and, crucially, just doesn't stay down. They both ended up being 'ejected' from the helicarrier in similar ways too. I never felt Thor was losing to Iron Man or Hulk, as he would keep getting back up from whatever he'd been hit with. As a huge Thor fan, this made me very happy.
In the other thread, otero commented that he thought Robert Downey Jnr was the star of the show. I disagree and thought if anyone dominated the film it was the Hulk. Everyone talking about the movie afterwards was talking about the Hulk.
If I had any complaint about the film it was the relatively weak opening action scene. There was a moment where I got a little worried. That said, this film masterfully upped the stakes and the action in a way that Thor, Iron Man and Captain America failed, with the peak occuring in the climax rather than earlier (Frost giant battle, Afghanistan and probably train scene, respectively).
Imagination will often carry us to worlds that never were. But without it we go nowhere. - Carl Sagan