How good or bad is it? I think his chin's pretty weak. Maldonado was able to drop him, Granados stopped him, and Ugas hurt him.
He took a lot of shots from Granados who is a really tough fighter, i don't see the chin question mark on that fight, Ugas has shown that he can hurt people, specially prospects, he has dropped most of his last opponents, some of them several times. I'm not saying that he has an iron chin, but a stoppage loss doesn't means a lot considering that it had more to do with conditioning and i don't think that Ramirez is the guy to expose a bad chin.
You answered your own question, it's glass - clearly. Only fanboys or glass jaw deniers would say otherwise.