I have used them since I started chickens, brooder to laying. All right its only been 8 months, but anyway!
I love them. Check out my page, page 2. Neil Grassbaugh, a member here sells them. Good prices and customer support, PM him. For cold weather I have 3 of them in a 5 gal bucket with a submersible bird bath heater in it. We'll see how it works this winter!
You may read how the chickens "don't get enough to drink". IMO if the chickens were still thirsty they would hangout under the nips all day. They don't, they tap the nip a few times then move on. Haven't lost a bird to dehydration yet.
Use a black bucket or paint one dark, cuts down on alge and slime. I also found the "Gamma lid" It afixes to any 5 gal bucket then allows you to use its threaded insert for easy access to the bucket.
I have used the "screw in" and the "push in" types. Use the push ins.
Good Luck