I tend to agree with SonOfThunder on this. I felt like there was a lot of implied history through the dialogue and acting that made what might have seemed like a "quick" development really the product of a long history prior.
Thor WAS noble already... he just needed a catalyst to kill off the self-righteous, selfish aspect of his personality and his exile, believed death of his father, the threat to those he had come to care for (Jane) and his inability to save them became that catalyst to recognize the necessity of looking to the welfare of others before his own wants and desires.
I think that's what made the film great, that they were able to build in a perceived history of past events that we never saw. Not much of that was in the script but the actors conveyed it remarkably well in my opinion. I felt like they were fully formed characters at a turning point in all of their lives.
I don't expect anyone else to agree with me but that's what I loved about it.
My ONLY real wish is a really minor aesthetic one... just that when Thor got his powers and mjolnir back that he'd gotten his helmet back too.
After beating the Destroyer, it would have been cool to see him walk up to Jane with his helmet still on so he was in his full-on Thor outfit and armor.