I've only used them for our cats (largely for when we brought Caeda home actually). They're not bad. One cat it barely affects though (but still helps), and the other one gets REALLY calm, as in only eats, drinks and goes to the bathroom, spends the rest of the time chillin in his "spot".
Just keep in mind that they do wear out. My personal preference is to not use them continually, just for short periods. The max for us I think was several days when Caeda got here, after that there was the odd day or two when the cats were skittish AND Caeda was being a brat. I think there may also be warnings on them for the age of the pet, but I can't recall....I personally would only use them on an adult/close to adult pet.