I've made a few peppermint soaps. I've used .75 oz ppo, but might up it to 1 oz ppo in my next batch... it's very strong at first, but the peppermint tends to fade as the soap cures.
It might be an irritant for some people, but it generally produces a cooling/tingling sensation on the skin. I use it just about everyday, it's great on a hot day or after a workout. Those who have tried mine like it as well.
Just be careful using it in your nether regions it's also pretty stimulating, I wouldn't shower with peppermint soap right before bed.