Hey Gals,
I had my mirena put in in February 2009. I just got it out three weeks ago.
When I gave birth to my son I weighed 230, having gained 50 pounds during the pregnancy. Two months after giving birth I was down to 190 and losing weight fine. All throughout the pregnancy and afterwards I was eating healthy and exercising, so for people who say its just because we eat poorly and don't change our diet after we give birth, thats not always the case.
Then I got Mirena put in. I gained all that weight back, horrible mood swings where I would start snapping at my husband over inconsequential things. I started getting really bad headaches, (I've never had migraines before, but I'm sure it was pretty close). Constant fatigue; I was always tired, no matter how much sleep I got and never had any energy to play with my son. I also hadn't had a period since February of 2008, just a little spotting after getting the Mirena put in. Not to mention discomfort during intercourse, which just made the act seem unpleasant for both of us.
Now that I've got it out I've lost 15 pounds, I no longer have headaches, All of my energy is back and I'm not as tired as I was before, and I finally got my period! I have never been more excited to have it than before.
I guess it works for some people, but with it and the hormones it was secreting, my body couldn't handle it. I've tried other BC's before too and didn't have any problems.