I had the Mirena put in 4 years ago because I forgot to take my pill and figured it would be a great form of birth control. My Gynie agreed even though I was 22 and have never had children.
I use to have lovely straight hair, I would literally just dry it with a hair dryer, no brushing nothing. Since I got the Mirena my hair went curly! I now have to blow wave, paddle brush and GHD my hair before it's straight. Proper curls people!
I gained 20kg in 10 months.
I also has severe stomach ache's that my doctor said was IBS, this went away when I had the Mirena removed.
My mood were all over the placed and my doctor put me on anti depressants. It was sooooo bad, I started cutting myself, hitting holes in doors and generally just crazy!
My breasts were so tender I could hardly touch them!

After a year, when I was single I decided that enough is enough and had it removed, luckily it wasn't painful at all! Not like the insertion which had me swearing and in tears.
I haven't lost any of the weight I gained but luckily I haven't gained any more weight. I'm currently on Yasmin and thinking that it's time to get off the hormones and see if the weight won't shift.

I also have a friend who has had no side effects with the Mirena but more often than not people do suffer badly. So please be sooo careful before having this put in and rather try a different from of birth control because the damage might just last longer than you expect.