I have one now, for 4.5 years; and I was just at my Gyn for my annual this morning, discussing removal (it only is good for 5 years) and what my options are afterwards.
Insertion was very uncomfortable for me. A close friend did not experience as much pain as I did (oddly enough, she is childless, whereas I have given birth). There was discomfort that progressively eased over the first few days, and the first few times I had intercourse. I was not advised to take anything prior to the procedure (but I will discuss that relative to the upcoming removal!). I took over-the-counter pain relief when I got home.
My partner at the time was fairly well endowed, and he never felt it during intercourse. None of my partners has ever mentioned feeling the strings during digital penetration, although I can feel them when I check to ensure that they are there.
At first there was irregular, but very light bleeding, then it was more regular, but still lighter and shorter duration. Prior to Mirena, my periods were moderate to heavy and lasted 6–7 days (even while on the pill). The past few cycles have gotten progressively more moderate and longer duration, so I guess that is because the progesterone in the Mirena is getting low. I have heard (possibly in a related question here on Fluther, but I can’t seem to find it right now) that someone got pregnant as they neared the end of the 5 years, which is why I wanted to discuss it with my Doctor today.
I am over 40 and my one and only child just graduated High School. I am done making babies (I had wanted more, but it didn’t work out that way). So I am considering permanent sterilization with either a tubal ligation or Essure. I am leaning towards the tubal, though. The NEW copper IUD is flexible and safe, and lasts 10 years; however, it often produces heavier periods, as opposed to lighter periods with the Mirena.
Google each, and read the safety information on their official web pages, and discuss with your doctor which is best for you.