I had a copper coil fitted after DS was born and loved it. My periods have never been bad and the coil made them heavier but it was manageable.
Then I had to have cryo-cautery on my cervix done and the consultant had to remove my coil and talked me into having a Mirena fitted instead. He assured me it was not like being on the pill - which never suited me - it was a 'designer ' coil, the hormones were localised and that my periods would stop. I said I liked my periods but it fell on deaf ears.
Anyway, I agreed and it was awful. I think they are the devil's work ! Mood swings, terrible cramping,spotting and acne. But far, far worse was the itching - it made me itch constantly - so badly that it woke me up and kept me awake. It's listed on the rare side effects.
I asked the hospital to remove it and they said no as you have to give it 6 months to settle. I thought bollocks to that and went to the doctor. When she looked it was nearly out and she said it would have been ejected with my next period. It took about three weeks and a course of steriods to sort out the itching.
So now I'm back to copper, but still have bad acne and my hair keeps breaking which is either stress or a reaction to copper. So might have to have that taken out too - had a lot of stress of late.
From what I can see, for some people with heavy periods its a godsend. But for me Mirena was a nightmare. I guess if you were okay with the pill you will be better than I was but never again for me.