I dunno if he's really a character thats hard to LEARN, but he is hard to play.
He requires very precise play, actual tech skill (and the melee player burst into laughter) and good reaction speed.
He is one the lightest characters in the game and dies pretty early, and has a pretty linear and easy to punish recovery if you arent creative with it. Basically if you make a mistake you pay for it more then you might with another character so you have to be careful.
All this makes him a difficult character to play well but its well worth the effort.
Also please try to avoid making new threads for this kind of thing, questions like this belong in the Q/A thread