He's hot headed and extremely confident of his ability and those, not his ego, often lead to underachievement and almost cavalier disregard for harder work on his own. Let us not forget that he was once motivated to do just that with coach Salahuddin after a string of failures, and became a significantly better batsman. Then he met coaches who pretty much gave him and Shakib an easy ride, and became intimately involved with Mssrs. Benson and Hedges.
I do not condone his immaturity, he is a experienced international cricketer representing his country, but understand it. I look at his age and the fact that he's surrounded by Nazimuddins, Imruls, Rockies, Nayeems and Omis of the world, guys not fit to play international cricket for any test playing country save us and Zimbabwe .
That being said, I don't think as he's egotistical as his brash persona and thoughtless comments lead many people to believe. He is generous to a fault and takes criticism well from true professionals he respects. Sadly, we don't have many true professionals who can fairly earn his respect in our cricket set up.
"And do not curse those who call on other than GOD, lest they blaspheme and curse GOD, out of ignorance. We have adorned the works of every group in their eyes. Ultimately, they return to their Lord, then He informs them of everything they had done." (Qur'an 6:108)