I had a Mirena for two years and I loved it.
I read all sorts of horror stories about insertion. When my doctor put it in, 6 weeks after my second child was born, I said, "That's it??" and it was. I sat up too fast and got a little dizzy, but otherwise it was no worse than a pap smear.
I spotted for a while, and my husband could feel the strings for a while, but over time the spotting stopped and I quit getting periods. Also, the strings "soften up" so eventually that isn't a concern either. It took about 2 or 3 months for things to even out.
If you look online you'll find forums for women who have had side effects. Just remember that those of us who didn't have horrible side effects don't generally post about it online! It's only the women who have had problems who take the time to set up forums. There's a real anti-Mirena bias online.
Removal was painless. However, I did bleed like a stuck pig after it was removed. I had terrible clots. The doctor's office said it was normal, but it was annoying. I couldn't leave the house! I tried several things to get it to stop. Finally what worked was drinking red raspberry leaf tea. It's a uterine tonic, and it helped a lot. I would quit drinking it and the bleeding would return, then I'd drink it and the bleeding would stop. I did this several times to be sure that I wasn't imagining a reaction.
I wrote about my experiences on my blog - http://prettybabies.blogspot.com - there's also info on how to contact me there if you have any other questions. Good luck!