As you guys know, I work at MAC, so I've used my time at work this weekend to investigate this mascara.
My final impression: Not all that special, and just okay.
It applies easily and fairly evenly in one coat. It dramatically lengthens and separates. I couldn't get it to thicken the lashes very much, which is important to me personally, so I wasn't all that impressed when I wore it on myself.
It lengthens even short lashes nicely, but they remain fairly slim and not very thick, so I wouldn't recommend this for people with very sparse lashes. I didn't notice much curl unfortunately.
If you LOVE the length and separation but are looking for more thickness, you could try Prep + Prime. I tried it on myself and customers, and it does add a bit of thickness, but not much.
Like I said, I am not all that impressed. I still prefer Prolong Lash and Plushlash. Those are my goto mascaras, and I have tried Lancome, Clinique, Prescriptives, Estee Lauder, Chanel, Dior, and NARS. People say they dislike MAC Mascaras, but I think you just have to try them all (at counter to save money!) and try them in different ways just to find something that works.