I had a series of 5 treatments, each spaced a month apart, back in 2005. I had moderate acne with some cystic acne on my temples and cheeks. My acne broke out worse for the first two months, which was my skin clearing everything out. The acne persisted, but gradually improved, for the 6 months following the first treatment (through the other five treatments). Within 6 months of the last treatment my face was acne free, which it hadn't been for 15 years!
I was told by my derm that I would need to come in about every six months for a maintainence treatment, but my skin remained clear until around august of 2008 - three and a half years!
My acne has not returned at anywhere near the old level, but over the last couple of months I have had very light breakouts - a level of acne that I would have killed for before the smoothbeam treatments. Nevertheless I will be going in for my first maintainence treatment (or two or whatever's necessary) to keep my skin perfect.