I bought all the bits to make one a couple years ago, then stalled out when I figured out I would still have to run it from a bucket rather than hooking it up to a pressurized hose/fresh water supply line. I think my peas would have used it, because I saw them drinking water "drips" off the wire pen enclosure when I sprayed water on the plants next to the pen. They seemed to like collecting the little droplets dangling from the wire.
One thing I hadn't figured out though, was the height to use. I figured I was going to have to experiment to see what height they liked. Also, I understand that the pressure on the nozzle can affect how easily it dispenses water -- a big reason I was going to need to use a bucket rather than a pressurized line. (Yes, I do know there are pressure reducers, but the pressure on these nipple waterers, to be effective, is in the low range of 1 - 2 feet, which is a really big reduction from house pressure here.) I wanted to use the pressurized line so the water would stay clean and I didn't have to scrub buckets.
I also think it makes a difference (or it may make a difference) which nipple system you use -- the vertical nipples or the little bowl nipples. I seem to recall @DylansMom (do I have this right?) was using the little bowl ones, and the peas would never operate the little toggle to get the water into the bowl. I bought the vertical nipples because the dust and dirt problems in my area would have instantly filled the little bowls with mud or caked clay -- not an improvement over the constant mud caking in their regular waterers. (Then there's the whole other issue of keeping it from freezing here...)
I actually think if you used vertical nipples and somehow got them to drip (at least initially), and you took away the other water source for a day or so, they would work it out. Once they find the dripping water and start poking it with their beaks, they can probably make the connection between poking the silvery nipple and getting water. Peas are more stubborn than stupid