The UGF is a controversial method, not unlike many of the other aspects of SW aquarium keeping.
I might actually consider using one when I change over my FOWLR, since I will not be using sand.
There are a lot of good articles out there, here is one. And it may surprise you to know some of the excellent reefkeepers around that have used them.
http://archimedes.galilei.com/raiar/lifttube.html