I use micas, oxides, and ultramarines. I love them! No problems with clumping so far, except for once, and that's because I added the powder after it had thickened to the point I couldn't SB anymore. If I'm going to swirl (such as it is, I'm kind of a novice swirler), I separate the batter very early on so each gets a good stick blending with the color in. That way I don't fuss with adding the pigment to oil/glycerin first or anything like that.
I've heard nothing but good things about labcolors though. Just haven't tried them myself because the pigments having been working, and this is such an expensive hobby already. :roll: