I've used their A2 flash hider before. It's nice, not great. The wrench slots do not line up at the proper 3-9 o'clock positions. Other than that, it appears well machined.
I will state however, that I'm doubtful they are really Melonite (or nitride) treated. Their advertising is tricky. When I bought mine, it was listed as nitride treated... then in lower fine print stated "black oxide coating" (which is a completely different thing) and mine DOES appear "black oxide" and not nitride (it definitely seems like a coating, not the nitride/melonite treatment). I don't have many rounds through it, so I can't comment on how the coating will hold up.
You may want to email them and force them to VERIFY that it's actually melonite/nitride TREATED and not just "black oxide" coated (many vendors love to "accidentally" use the incorrect terminology, especially since "melonite" and "Nitride" is popular at the moment).