birth control
"I had Mirena for 4ish years.  I had no pregnancies and almost no periods, which is exactly what I wanted.  

I did have to make an OB appointment and have a quick ultrasound to check it once.  I felt it move somehow during sex and then had a bit of bleeding.  OB confirmed that it was just a scratch and not a uterine puncture or anything major.  The other downside for me was sexual side effects, most notably "diminished arousal response"

Even with those two negatives, I would get Mirena again if I were in a position where preventing pregnancy was essential."