I had bad acne when I was a teen; it turned out that it was mostly caused by being sensitive to soaps and different stuff.
As I got older, it went away. I still get some even though I'm on HRT -- actually, I get a "monthly" zit usually on my jaw line or chin. Natal women get them as well during their periods as well. I don't know if the general mtf trans population get it, however. I just know I do, and so do my roommates, and a lot of other women I've talked to.
One thing that helps is use a moisturizer with glycolic acid (I use 10% nightly, but you may want to start with a lower concentration, like 4 or 8 at most until you get used to it) and it can help clear things up and also help to heal old scars, improve the tone and texture of your skin, and the elasticity and moisture level of your skin. Most people notice a change pretty quickly, and it just continues over time. I know I've had a change in my facial skin appearance and I've had comments on it and I've been giving the tip out like mad to other women who keep asking me what I'm using. Even my psychiatrist wanted to know. (I use Neostrata, personally, although Reversa also has similar stuff and I hear it's good, too).
--natalie

PS wow did that last part ever sound like a marketing pitch. LOL!