Like Orion said, they (Or any HOB for that matter) are not the best option for fry.
Fry aside though, you'll get mixed opinions on them here. Some people praise them, some think they're junk.
Personally, I've owned one and my sister has owned two; all of which were traded for Aqua Clears. I don't think they're all out junk, but I do think there are much better filters out there, in terms of performance, design, and quality.