I'm taking it right now. You don't notice it at first, but it does make a pretty good difference. I say pretty good because I didn't have extreme acne to start with; I got one or two big red sores usually on just my cheeks and the odd pimples on my t-bone area. Needless to say, the sores are gone!
It's not a miracle cure, but I expect it takes away the worst of things, at least from what I've experianced myself. I've been on it 3 months now? That, on top of a over-the-counter spot treatment and dove baby soap. Remember to drink lots of water with it, at least a bottle, and be wary it makes you photo-sensitive and to wear lots of sunscreen. Also, like most antibiotics, it can have some effect on birth control pills.