I heard some not so good things about it, and I've heard some really bad things about it.
My Skilter experience:
A local reefer was emptying out his closet recently, so I bought a grab bag of reef goodies from him. Included was a Skilter. As mentioned above, I never heard anything good about it, so one day I decided to pull it out of my closet and experiment to see how it would perform on my tank. For reference, my Remora skimmer pulls a full collection cup about every 7-10 days. I put the Skilter in place of the Remora for 10 days and got NOTHING in the collection cup; just some large bubbles in the bubble chamber. Back into the closet went the Skilter!