UGJ's are great! Its a great way to keep debris from settling in the tank and to rid a tank of dead spots. I have one setup in my 29 gal tank and i get very little waste when gravel syphoning.
I agree that it is somthing that you should plan ahead for before filling up and starting a tank. You need to know how you want the outputs to flow in the tank, how many outputs, size of the powerhead to get desired flow through each of the output jets. Its also a good idea have time to epoxy substrate to the outputs so that you don't have to look at the ugly white piping.
can't even tell its there.