I went on the pill to help my mentrual cramps when i was 16. It didn't really help the cramps that much but it did give me a lighter flow which was great because my flow was super heavy before going on the pill. Then about after a year of it not lightening my cramps my doctor put me on seasonique which only gives you four periods a year. That was nice at first. It didn't lighten the cramps but having cramps only 4 times a year was definitely better than having them every month. But after about a year on that i started getting breakthrough bleeding that would last a whole month. I didnt have cramps but the bleeding was annoying especially during the summer. so then when i was 19 my doctor put me on the depo shot and that stopped my period all together which was soooo nice! my worst side effect was that my sex drive slowly decreased. I was on it for three years and by the end of the three years i got off of it because i got married and my sex drive was totally gone. that was one year ago. it took 6 months for my period to come back and when it did it came every other week with cramps, which was super annoying. that went on for about 3 months. now i am back to a normal cycle, my periods are still lighter then they were before i went on the pill but my cramps are still bad. i am also trying to get pregnant and have not had any luck. I am hoping all these years of birth control didn't make me infertile.
I do know these things differ from person to person, birth control might work for you. But that's my story.
Positive: quick fix and is quite effective. It's fairly good in many respects :)
Negative: if you have antibiotics, diahhrea or miss one day it won't work properly for a little bit - so don't freak out but be aware when things randomly happen that shouldn't happen if your on the pill. You also may not get use to the pain so when you go off it if you ever want to have kids or something, it might be difficult adjusting - but that's not really a problem ;)
Sorry, that's all I know about it :P