I had my Mirena put in back in January 2006. I have a fantastic specialist doctor D. N. in Melbourne. She put mine in under GA, which after reading other peoples experiences I am so grateful for.
Obviously I had no pain having it put in, just a very short light GA, then home as soon as I woke up.
I had, what I could best describe as bad period pain and bloating for 8 weeks and seriously regretted having it put in. I called the specialist and she gave me a script for some antibiotics as she believed I had an infection. As soon as I had the antibiotics my body settled down and I have never had a problem since.
I would highly recommend the Mirena, but I would also recommend getting it put in by a specialist and give your body time to get used to it.
Before the Mirena I tried all the different pills and my body reacted very badly to them, (weight gain, lethargy etc). I have had nothing like this with the Mirena, I have had light to non-existent periods and almost no period pain. Don't be scared ladies, just get a good specialist.