Please understand that I know that I am in the minority; but I also know with absolute certainty that I am not the only one - probably closer to the 10% mark.
I had Mirena inserted at my 6 week checkup and removed just before my son was a year old. I cramped and bled - sometimes for days in a row, sometimes I would have a day or two off, sometimes every other day - from two weeks after placement until four weeks after it was removed. Sex was so physically painful (I went through labor with no drugs) that my husband and I only did it twice in that time period. He couldn't bear to see me cry.
I had to have another doctor remove the IUD because my doctor's office kept saying, "mirena doesn't cause those symptoms". That may or may not be the case - but when it was removed, it was a sharp pain and a foul odor, and I had purulent (pus) bloody drainage for a couple of weeks on antibiotics. It cleared up, I had a hsg (fluid filled ultrasound) to ensure there was no long term structural damage to my uterus. I was diagnosed with an auto immune disease (which results from your body being in a constant state of inflammation - what the IUD is designed to do), which is under control thanks to medication and have since had another child.
I would not recommend Mirena to anyone. Well - maybe my husband's ex. But I really don't hate her enough to wish that kind of pain on her.
Just My Experience.
S.