Obviously imo he is a great trainer, but the guy was a complete wanker. Talked a lot of bollocks and was incredibly arrogant.
As has been said. Great motivator, will get you in fantastic shape. But i'm not sure how good he was at the actual boxing training. Things like strategy and teaching. He certainly wouldn't be my first choice if i had to send a young kid to learn boxing from someone. I don't think overall he's either underrated or overrated. In a way he was fortunate to give birth to one of the best fighters of his generation, who could adapt on the fly. Enzo was a perfect fit for Joe though because he didn't/couldn't try and change him. Maybe if Joe had a 'traditional' boxing trainer from the get-go some of his naturalness would've been trained out of him. Joe was one of those fighters who did things that even he couldn't explain to you. Enzo played a big part in encouraging and enhancing that and he was also brillient for Joe from a mental point of view. Unfortunately what works for a special fighter like Joe is not ideal for everyone else.