I have experience....I experienced the horrible skimming abilities and threw it in the garbage. I did get good use from the tiny pump it comes with. Got that in my 2.5g nano, but wasn't worth the purchase of a fission skimmer just to get the pump.
They will decrease in efficiency very badly with decrease in water level. So using it with a sump is an almost must. And if that ain't bad enough, they have these ring/cotton filter inserts that you use to decrease microbubbles....I say decrease, cause they're always there no matter what you do, and then you have to buy more little filter ring replacments often.
Save yourself the money and do an extra water change.