I used to drink green tea every day and I experienced no benefit whatsoever to my skin--in fact, i'm pretty sure it made my acne worse due to the caffeine (my doctor was the one who actually pointed this out).
I don't know what the reviewer down there is talking about when she claims that green tea regulates her hormones...it's far more likely that she stopped breaking out due to the fact that her body finally adjusted to the birth control and hormones her doctor put her on...
I like to use it topically, sometimes as a toner, sometimes as a spot treatment. It totally kills the inflammation on your face, which works wonders for any cystic acne you have. Seriously. Have you ever had a big red inflamed pustle/cyst on your face and then had to resort to taking advil to make it less inflamed and noticeable? I have. It totally works, but usually when the advil wears off the cyst blows right back up worse than ever. Green tea is way better, and sometimes it can help them go away or come to a head a lot faster. I'm not sure how it does it, as it causes no irritation whatsoever, but I could swear that it even seems to help dry them out sometimes.
Green tea oxidates over the span of hours, so don't bother leaving it around too long. I leave it brewing in a sealed travel mug for a couple of hours and then use it as a toner after washing my face. Then I use it again in the morning (my travel cup is metal and so tightly sealed that it's actually still warm by the AM otherwise I wouldn't use it).
Brewing it in boiling water and using longer steeping times increases the polyphenols---though this makes it taste like bitter crap, so keep that in mind if you're going to drink it.