I tried the Mirena and it didn't work. I didn't get pregnant or anything, but I was sitting on the toilet one night, sneezed and it fell out into the toilet. (Sorry for the TMI). I had it in for about 6 months and had maybe 3 weeks of no period, with bleeding the rest of that 6 months. I hated it.
I've heard of it when I was choosing my birth control method. I didn;t choose it because it doesnt really do its job. It doesnt prevent you from getting pregnant. You could still get pregnant except that you will shed that already fertilized egg. I couldn't think of living with having miscarriage after miscarriage. So that'll never be my birth control method.