In terms of the character itself, I can't really say that I find anything really difficult. I enjoy the character so much I don't perceive difficulty in trying to be him. It's just a matter of how do we get there.
I think if you are going to be a singer, you should sing. If you are going to be a dancer, you should dance. If you are going to do a combination of the two, you should make it very clear when you are singing and very clear when you are dancing.