Skill-wise he's a world class fighter. I think he's around 9-10 P4P.
Aside from his conditioning, or lack there of, between fights, his main weakness seems to be his mental make-up. He lost his composure during the PBF fight, and he's been making excuses for the outcome and moping about it since he picked himself up off the canvas. As long as he sticks to the 140lb division and doesn't rematch PBF, I can see him finishing his career with the loss to PBF the only black mark on his record as he's clearly (IMO) the best Jr. Welter around. I think Malignaggi gives him a hell of a fight though.