I have 2 yo-yos and have kept several over the years. The first bunch I had many years ago were really quiet and great at snail destruction! So this time round, I bought a small pair - they have grown to around 2 1/2 inches and are voracious feeders! They prefer flake to snails now (lazy) and I did have to put them on a diet at one stage, as one got really chubby.
I also have to be careful with mine, if they get hungry they will attack smaller fish and kill them. In fact, I think they were responsible for recently killing my Chinese Algae Eater (who was bigger than them!!), but he was a fussy eater anyway, so it might have been a combination of things. They cleaned up the mess anyway. They don't mess with the Dark Ruby Barbs I have though.
Generally, I like them and they are entertaining. If I put my hand in the tank, they come along and try to tuck into my hand - and you can really feel it! I'm glad they dont have teeth!