I use them. Whats the bad side of them? Only last two or three times after wash, but only like for a week. I like that they make my sump not sound load.
I have like 6 pair. I change them out with every water change, or if they begin to over flow. Just turn them inside out and wash with vinegar , let air dry, and use em again. I have one pair that is got to be 5 years old.