I can't believe these forums exist. I'm writing from work right now, wasting company time. The Sigma brushes arrived in the mail this morning. I purchased the Sigma professional premium brush set kit, the one with 15 brushes. Before heading off for work, I took a few minutes to test them out, even comparing them to my (incomplete) mac ones.
First off, they are pretty soft, especially for the price. The first one is a large brush, the F20. Soft, dense and fits the grooves of the face. I know it's heresy here, but there's little to no difference to the equivalent mac one.
Then there's the Sigma tapered face F25. It has a nice teardrop shape. But not nearly as dense as the mac version and has noticeably fewer bristles. When you press it against your face, it does not hold its shape as well as the mac one. But in its defense it is pretty soft.
More posts later, as the evil boss may be returning anytime.