well, I don't know if I'm loyal or disloyal. I mean MAC is a line of make up not a person, so it's not like I have to commit to it :/
Now, most of my makeup is MAC, because the price is good for the quality I get. I have many MAC eyeshadows, pigments, paint pots, lipstick and lipglosses, plus a few blushes (ever since they released their mineralize blush and beauty powder blush)
The only things MAC that I don't like are their skin care, foundation (for these two I go to pricier brands), mascara (Cover Girl is good enough for me) and nail products (OPI all the way).