Well, considering I'm one of his staunchest admirerers and defenders, I'm assuming you're talking about me?
I think it's the opposite; that he's underrated by those who don't like him.
I have yet to hear anyone of the #MatriBelievers claim that he's fuoriclasse or even very near to being that. All we're saying is that he's a fine striker. We don't claim that he's better than Trez, Cavani, Suarez, Benz, Balotelli, Higuain and the likes. Most of us are just annoyed that people didn't give him proper credit for his contributions to the side.
Llorente is a better striker, too, but I feel that Matri will give him some competition for a starting spot, and that's a good thing for the club.