I have had the Mirena for a couple of months with a very little amount of spotting. I got my first period about a week after insertion and it lasted about 12 days which is much longer than usual. After that it's been extremely light not even requiring a pad or tampon. I haven't had a period since then and hope I will be one of those that never do again. I haven't had any other side effects that I have noticed. The one change I made is switching from Proactiv which uses benzoyl peroxide to Neutrogena products that use salicylic acid. My skin has cleared dramatically since the switch. I am actually getting off the anti-depressants and haven't noticed any mood changes that I can attribute to the Mirena. In fact, I'm less moody possibly due to my hormones finally becoming balanced and steady.
I chose the IUC because I was sick of taking a pill every day or slapping a patch on my butt once a week. Also the pills made me gain weight and I became allergic to the adhesive on the patches. The Nuva Ring was very uncomfortable and caused cervical swelling. So, after talking with my doctor this was my only choice because I have to have some form of birth control due to absence of periods and possiblity of fibroid tumors.
I admit I haven't had the IUC as long as others who said their symptoms appeared after years so I can't be sure I will never have problems. I'm just praying for the best and hope I'm one of the 90% of people who had no problems at all. I hope you have the same good experience that I have had so far.