I liked Norton's Hulk. Avengers Hulk looks fan-frickin'-tastic though.
I would love for Hulk's first words to be in response to some smart ash Stark comment.
In regards to Hulk/Thor confrontation, I think the best way to portray it would be a game of 'I can do one better'. Start it out with Hulk thinking he(thor) is some 'big-but-puny' Human and Thor having that bit of arrogance that he had in the beginning of his solo movie.... have hulk punch thor, thor whacks hulk with hammer, and so on.
Finish it off with Thor getting the final blow while also showing that Thor can obviously take a punch. Something along those lines would be cool
I felt in "Thor" we never really got to see the extent of Thor's durability in his movie. He destroyed the Destroyer as soon as he got his powers and I never really thought of Thor being in any sort of real danger when he fought loki in his final battle. Still a great movie, it's just something I noticed, imo