Yeah-- some people like them because birds can't make soup in water food (or poop in it, in a multi-bird setting), but I don't like them because of clogging, cleaning, bacterial potential---If you stay on top of them and clean them REALLY well each day (with proper bottle brushes), and make sure they work each day, they can be okay..But people tend to fill them up and leave them and then bacteria gets inside when the bird licks, or the dispenser gets clogged so it looks like the bird is drinking, but no water is actually coming out.
Plus, some birds do not know how to use them and that is another issue.
I am not saying they have no benefits, but I wouldn't use them for mine (due to the worry of the ball getting jammed, clogs, bacteria etc...I just feel like I am more accountable about changing water and washing the dish without one. I know they are a pain to clean properly because I used to have one for my guinea pig growing up and I definitely should have changed it and washed it more often...the water LOOKS clean, but it isn't necessarily...so they need frequent attention