This is only the beginning for Chiaki´s career with this new orchestra. Yeah, the performance wasn't perfect, but I think it was fair enough because of all the disadvantages: not enough time to prepare, a foolish manager, a stubborn and overcontrolling concert master, changes of last minutes, etc, etc.
Nodame sensed the failure, so that's why she allowed Rui to play the celesta. However, I hope she could also understand, even a little, that Rui also has her own problems and in some way both are similar (too bad that she didn't know that Rui listened her piano and it made her chilled because it has what she lacks).
Also I liked the pieces played for the exams, I listened to them in YouTube while I was reading certain parts of the story where they are played in the manga. The surprise is that Nodame already has plans for her summer vacations, where obviously, Chiaki will go with her.