Like a few have already said, his performances up until his injury were average to good for him. He's goal kicking accuracy seems to have improved. But he's awareness and decision making is still far too inadequate, as is his tackling. Also he still struggles to take clean possession of the ball down low.
I don't like fans jeering him, it's counter productive. I'd rather fans express there thoughts to Simon in other ways like, "we want Cam Pederson in the first team!', or something else positive.