I was on Yaz for almost two years. Just under a month ago I switched to Diane-35.
Honestly, Yaz didn't make much of a different for my skin. In the first few months my skin was slightly better, but then it went back to "normal" (ie: acne), and for some reason, just under the 2 year mark, I broke out worse than I've ever broken out before in my life.
Between the couple of weeks of "better" in the beginning and couple of weeks of "worse" at the end, there wasn't any significant improvement or worsening.
Hopefully the Diane will sort my acne out, it's my last resort before trying Accutane.