My only problem with him is he's too weak. Kaguya should've made him from a TSB with her will and some jyubi chakra. That way at least he wouldn't have been fodder.
I personally liked him. He was a good addition to the list of villains and his skills were mysterious. He was also a technically a spy inside Akatsuki itself, lol. He was only truely loyal to Kaguya xd
I did not care about him much, I simply wondered why there is White and Black. And actually, when he was part of all this in the end, I loved him. Too bad his spotlight was short in the end, and also, I would have liked to see more battle scenes with him. afaik his fight against Mizukage and her shinobi was the only one.