I've been using this for about six weeks now, I upgraded from once a week two twice a week just recently and it really starts doing its thing. I'm using it because I do have visible signs of aging a.k.a. wrinkles especially on the forehead and I would say these have been reduced by about 60-70% by now. I use it on a buffering layer of moisturiser so the "uglies" didn't get out of control.
Not much besides the usual side effects of retinol products. When I upgraded it to twice a week, I started to peel and get blotchy on rather dry/sensitive areas of my face. Nothing a good moisturising routine can't get rid of.