I have tried it before, and I tried it only a couple times because I realized that you almost have to build a team around it. It's hard to just throw it on to spam sleep, unlike a pokemon like milotic. You need one that can for one, take advantage of the sleep, so a bunch of intimate pokemon aren't amazingly helpful. And, number two, be able to help dodge around protects that go up. Also of course as you mentioned, prediction, which is a huge factor. Even though I used it early, when I wasn't very good, from my limited useage of it it can definitely help sometimes, but overall there are better pokemon. (Plus random goggles to stop other Pokémon's sleep powders and sandstorm chip). Also it fails against koko and fini, both of which are pretty popular