You can follow my tale of woe here. I had a Mirena for 8mos and had it removed. I had pretty normal periods before, and didn't react badly to other hormonal BC, and ended up with constant spotting, annoying side effects, and a 4cm simple cyst on my left ovary (that did resolve after IUD removal). My experience isn't necessarily common, but I don't think it is uncommon either. I really wanted it to work for me and was so so so disappointed that it didn't.
Mom to two amazing DDs ('07 & '09) and a fur baby.
Gluten free since Nov '11 after non-celiac gluten sensitive diagnosis. Have had great improvement or total elimination of: migraines, bloating/distention, heartburn, cystic acne, canker sores, bleeding gums, eczema on elbows, dry skin and scalp, muscle cramps, PMS, hair loss, heart palpitations, fatigue. I'm amazed.