Hiya,
I had the mirena for just over three years and in the end had it removed due to increasing side effects. It is different for everyone and although it hasn't worked for me and (four of my friends I have since found out) my doctor swears by hers and loves it.
I bled for the first 10 months continuously and then just had light monthly periods, my periods only stopped just before the 3 year mark prior to me having to have it out.
My side effects included the following: Muzzy Brain, lack of concentration, lumpy extremely painful breasts with led to mammogrammes and ultra sounds, re-occuring thrush, baby like movements in my tummy, arm pain, heart palpations,migraines, mood swings, numbness in toes on one foot... all of these can be explained away by themselves but once I did some research I was astounded by other womans symptoms. I can search out a web site that I found that is a forum for women suffering from this IUD if you would like to have a look. There are a number of accounts of the IUD being lost and turning up in strange places inside women, many women getting pregnant whilst they have them. Alot of woman are suffering years after having them removed, there are many law suits across the states regarding this IUD some are trying to get it band, as I say for some woman they are wonderful but please do your homework before going ahead, the say fore warned is fore armed so I thought I would just let you know my experience.

Take care
Missy