I got Mirena after my second baby and thought it was FANTASTIC! I never even started my period back and there seemed to be no side effects and no weight gain. I was worried about side effects because my libido plummeted with BC pills but the Dr. told me that it is such a tiny amount of hormones and it is delivered so locally that I shouldn't have any problems.
I've always had about two to three Migraines with aura a year tops. But about three months with Mirena I started having one, two, or three a month with no meds helping. I tried everything and finally I got my Mirena out. The following month I had three migraines and thought I was back to square one. But then they went away. I haven't had one in four months! I think that the hormones took a while to get into my system and then took a while to get out. I'm now using Paraguard and although I have heavy painful periods at least I can take meds for it and there are no hormones!