Hi elle, i've been on diane-35 for about a year. It has made my skin beautiful and perfect, I love my skin now. (i had moderate acne on my face and back before, which I hated.) it took about 7 months to go away completely though. Also, since the pill has taken all the hormonal grease and oil out of my skin, it has also taken it out of my hair and I only have to wash it once every 3 days.
The seven final pills in the 28 pack contain no hormones- they do absolutely nothing, they are just to keep you in the routine of taking your pill at the same time every day. The 21 pack just eliminates them because they are not necessary for your contraception to be effective. I usually take 2 or 3 21 packs in a row to skip my periods for a couple months.
I would like to switch to a different pill soon, as the diane has a slightly higher blood clot risk, but I am very afraid to come off it because I really can't take breaking out again. I don't want to be a slave to the diane forever though, so i'll have to try soon.