When I first started using Proactiv I virtually stopped breaking out. When I did, they were just tiny little white heads, which really didn't bother me. It's sick, but, I kinda thought they were cute. haha Easy to get rid of, anyway. It took about a week or two for my previous pimples to go away. Then I was pretty clear and happy with it.
Then I got lazy and didn't use it twice a day and I started breaking out again. I stopped using it for a long while because frankly I didn't really care. But lately I've been breaking out a lot.

So I decided to start using it again a couple weeks ago. I don't know what the deal is, but it didn't stop my break-outs until these past couple of days. My theory is that if you're stressed or something, the product isn't just gonna stop everything.
About irritation, at first the toner stung and made me feel dry. But putting on the lotion felt like a moisturizer so it didn't bother me much. Now I'm totally not irritated by any of it. I know that my brother wouldn't use it though, because it gave him a rash or something.
What had been bothing me for a while though is how the cleanser just doesn't feel like it cleans you very deeply. But maybe I'm wrong. Maybe the fact that it is gentle is best of all. It has very gentle exfoliating beads, which I think is good. It just gently exfoliates you day-by-day, so you don't have to do it harshly once a week with some other product.
It may not be the greatest thing for everyone, but it's worked the best for me out of anything else I've used. I've had acne since I was like 10 or 11. The biggest problem I had at first was making it a habit. I wasn't used to doing the whole thing twice a day, but now I wouldn't live without it.