He is a decent character I think. Someone who was trained to have no emotions and who has to slowly learn becoming a human being again instead of some mindless assassin.
His design isn't great, I agree, I hate his shirt but all in all, he is handsome and sweet.
The more he learns about feelings and friendship, the better he will handle his life and become normal. Yeah, he started off weird but now he is just funny, enertaining and cool. He is becoming a true friend and he will make up for what he is missing. The episode with his brother was just sweet.
I think Kishi didn't create him to be a new Sasuke. He created him so Naruto learns accepting new friends and getting over his old obsession. He was also created to show human nature and how it would affect someone to be treated cruelly like Sai was. As I said before, he is an interesting and deep character.
