The most underrated? Hardly. He is indeed awesome on the mic, I'll give him that. I've never been a fan of his matches though. I legitimately tried to give the guy a chance despite not liking him at all up until he tag teamed with Morrison. Even then I was upset that Miz got the bigger push out of the two. I still gave him a chance. He then won the WWE Championship, a moment that caused the wifey to boycott the federation and her fandom never recovered. I hated it that he won a title I never felt he was believable holding, but still gave it a chance.
He defeats Morrison.... again.... and then moves on to feud with LAWLER!? A guy who never should have been a world champion to begin with was feuding (on PPV, mind you) with a retired announcer. The WWE Championship has never taken as much damage to its prestige as it did that month. Miz went on to main event at Wrestlemania 27 by retaining against Cena. He lost the title to Cena soon after and went on to team with R-Truth in the Awesome Truth. That was a team I liked. They split up too soon though and later on Miz turned face. Awful decision by WWE. I still continued to give the guy chance after chance, but it's just not working. He is in need of a heel turn, he's best at being hated.
Miz is best in a speaking role. I have zero issues with his promos. If he stopped working matches and only did MizTV to help further promote upcoming matches, I'd be happy. Maybe he could be GM or an announcer some day. It's his matches I have a problem with. I struggle to ever find any interest in one and he to this day is just simply NOT believable in being anything more than a midcard title holder. I gave him multiple chances but have come to the conclusion that it's never going to happen. Miz is not world title material. What I hate the most is that WWE invested so much into his push in 2010-2011 but then just threw it all away by making him do unrelevant angles for so long afterwards, let alone the awful face turn.
Shorter version: He's awesome on the mic, but not in the ring. He is also a far cry from being underrated. I do give him all the credit in the world for trying his best to improve. It's WWE's fault for not following through with such a huge push and for pushing him in the first place when he is not (and never will be) believable in any role further up the card. Make him do just MizTV segments from now on, that's a better role for Miz to showcase what he actually is good at.