I too am a MAC believer! The trick with MAC makeup is to go to the counter and have someone do your make-up. However, make sure it is someone who will do WHAT YOU WANT. I have a "MAC girl" now, I swear by her, for every occasion I explain what I'm going to, what look I'm going for and she is amazing. Sometimes if you go to their counter their associates tend to have very bold dramatic make-up and this can be disconcerting. I had gone to one girl previously who wanted to put me in royal blue eyeshadow.
As with any makeover the trick is to find someone who has their make-up like you would like your to look, since most people apply make-up on other people similarly (is this a word?!?!?) to how they apply it to themselves. But again, I swear by MAC makeup it really is wonderful and stays on ALL day.