I think he needs serious work on staying in rhythm, his pocket presence, accuracy, and needs to stop forcing balls. But I do think he has talent and at times he looks really good. But that is all to often broken up by a terrible interception or a long streak of inaccurate passes and taking sacks he should not take.
He's just very inconsistent which makes him all the more frustrating because you see glimpses of his talent but he hasn't put it all together and I'm not sure that he ever will.
Anyway, I also think that Kelly's offense is pretty bad and outdated. And the inability to run the ball consistently is not doing Nuss any favors. They break some big runs from time to time, but they can't consistently run the ball. I tend to think that Kelly's offense only really works with a QB that is more mobile than Nuss.