While I don't disagree with the never enough power bit - the Cor 15 works perfectly fine. I run one and it performs equally as well as the Mag18.
I chose to run a Cor 15 because that is the same as my return pump. If for some reason my return goes South I can take the skimmer offline and replace the return pump in less than a minute. Maybe I should clarify that for me, it works fine and I didn't see a difference in what it collected between the two. The only difference was the Cor produced less noise. Maybe I have less bio load, younger tank, or magical pink unicorns - just an opinion.