I've got it too, not a severe case, but I am definitely aware of it.
All the symptoms previously mentioned, for me, pain was always localized to one side, like one ovary had a bigger problem than the other. I knew in my gut that's what was wrong. I have always had heavy periods and severe cramping, often had to stay home from school when it was my time. In 2004, I started having intense pains and trouble, kept getting dismissed by my ob and sent to specialists for all kinds of other things. Finally in 2007, I started seeing a great ob when we had moved out of state and she agreed that I had the telltale signs. We discussed it in length and determined the best thing to do what laparoscopy. She removed a good amount of scar tissue on my left side, the one that had always hurt and the diagnosis is what prompted me to stop putting off having a baby.
Pregnancy and nursing have kept it at bay and I too continue to nurse, partly because I know it will help. Birth control has always helped with my symptoms to a degree, but not eliminated them. My ob told me that the best thing you can do for it is be pregnant, nurse as long as possible and then get pregnant and do the same thing again. Great if you want a lot of kids I guess!
My best friend has a very severe case and has gone through tremendous pain, multiple DandCs, losing a baby at 7 months...just heartbreaking stuff. Now, at 35, she's having back problems related to it.
If you suspect or you are diagnosed, I highly recommend staying on top of it. It does tend to worsen with age according to my ob. I don't know of any link to cancer, but can cause abnormal paps.