I definitely love and would recommend MAC prep + prime lip for anyone that wears Mac lipstick. Lipsticks last longer when prep + prime lip is applied first.
I've tried so many different primers, but this is the one that actually works. It doesn't dry my lips, or make them flake, and my lip product stays on very well! I don't use "all day" products as they tend to dry my lips, so I do have to reapply after eating, but this primer keeps my lips looking great right up to lunch, and then again up until dinner!