Sorry to be a downer, but you should know that even though they are much safer than they used to be, they still aren't perfect.
I had the Mirena and I will never ever do that again. Getting it inserted wasn't that bad. However, it wasn't comfortable. I could feel it and it was painful at times. A couple months after having it inserted I'd had enough (pain plus I couldn't find it the way the dr had showed me to feel for the strings) and went to get it out.... except the dr "couldn't find it". She tried, as well as a few other people from the office. After about 45 minutes of excruciating pain it was decided that nobody knew where it had gone. I went to have an ultrasound, where they did find it (along with the reason why they couldn't find it.... turns out I have a didelphic uterus (double uterus) so where they thought they put it, they really put the mirena somewhere else). So back to the dr I went with this new info. Again, they tried to get it out. They did, eventually, but it hurt so bad. Never ever again. I'll willingly take a pill every night!