I had the Mirena IUD, and it was horrible! Yes, my periods got very light, almost totally gone infact (who wouldn't like that?). However, the negative side effects were nearly unbearable. I began to have migraine immediately after having the device implanted. I would have upwards of 5 dibilitating headaches a week, started taking powerful drugs to prevent and treat the migraines, had an MRI, but nothing helped them. I couldn't function, let alone take care of my kids. I also had terrible back pain. It would seize up whenever I laid down, and it would take me 15 minutes just to get out of bed in the morning. My OB/GYN wouldn't listen, kept saying it was not related, however, after a year I finally insited they take it out. My symptoms dissappeared with in a week after I had it removed. I would use caution with the Mirena. Well, actually, I would use caution with any IUD for that matter. It's a foriegn object and my body fought very hard against it's presence in my uterus. If you do choose it, listen to your body if it has a bad reaction. Don't wait to see if you adjust.
* After my experience with the Mirena, I opted for natural family planning. I read a great book called Taking Charge of Your Fertility, which shows you exactly how to avoid or how to get pregnant by knowing your body and your cycle. It can be a little regimented at first, but once you know what to look for, it really works!