I bought this in a moment of desperation when my super duper oily skin was going through an unusually bad flare-up of cystic acne. I get this monthly--thanks hormones! I thought maybe I wasn't exfoliating enough, so I bought the Mia to help cleanse my skin and get the gunk out of my pores. I had heard of the dreaded Clarisonic "PURGE" phase, and hoped no such thing would happen. It seems that the Clarisonic merely broke me out, and never improved. When I stopped use, the severe blemishes healed up pretty quickly. Although touted as a helpful tool for preventing acne, I do not recommend this tool for those with sensitive and blemish prone skin.
It's been about 5 days since using my Mia and I may try to use it again, and monitor my results. Of course, no one wants to give themselves acne, so buy with caution and know that it might not help you.