Guly is one of the top goal-scorers in the league and his rate of assists is pretty good too. Yes, he can be immensely frustrating to watch... then he'll go on and do something marvellous shortly afterwards.
Booing one of our own players is ultimately self-defeating. Cheering them on builds their confidence and leads to better performances. If there are problems with Guly's play (and I think we would all agree that he is not the complete player yet), then it is Nigel and his coaching staff to work on any shortcomings in his performance on the training ground. Disparaging our own players will not increase their performance levels.
Repeat after me: Ole, ole, ole, ole, Guly! Guly!