I've heard a few bad things about royal grammas, or at least I think I have. Do they get mean, or pick at some corals?
I would know if mine was mean or not, the only other fish I had was a bangaii cardinal. The gramma didnt nip at any of my polyps that I saw and i would think it would have been noticable... That's not to say they don't do that, I just didnt experience it myself. I had a mixture of most different types of corals at the time. (at least the ones we see in the hobby)

-Brett