I'd imagine he would have got fed up being dropped for big games or not being picked for Scotland. I don't recall thinking he had a bad attitude.
His biggest problem was the demise of 442 formation. He's a fantastic finisher, but not much use running into channel's. If you could swap him and McCoist era's, Ally would have the same criticism leveled at him, and Boyd would have been just as prolific as Ally was.
Imo.