While the decision was grumbled about fairly loudly, I feel that changing the actor from Edward Norton to... this fellow who's name escapes me was one of the many correct moved the movie makes. While Norton can sort of pull off the "puny, mild-mannered Bruce" routine and portray the Hulk as something nightmarish, this actor conveyed the sense that being Banner is the scary part of his life, always on the run, always feeling the Hulk in the back of his mind, and with the certainty that one heartbeat too close to the last is all that separates his immediate vicinity from a disaster zone.
That, and the conservation of Hulk episodes (he only had two in the theatrical run, at least,) really makes Banner the star of this duo for once.
Interesting -- we still need to have the skin tone talk! I think this is a pretty good choice for Ruffalo based on reference pics, but I oddly have this impression of him as being more obviously swarthy. Hmm.