I had three Mirenas over the course of about 9 years. The first two were perfect, with no side effects and stopping my periods.
For me the insertions and removals were fine. Maybe a 3 out of 10 pain wise and some mild cramps afterwards. Unfortunately I know that's not everyone's experience.
After about 3.5 years of each Mirena, I got lots of breakthrough bleeding and my GP decided to change it early to prevent this.
Unfortunately my third Mirena gave me unpredictable bleeding for months, which was affecting my life as I was always worried I'd bleed through clothes or during sex. I also kept getting recurrent thrush, which I'd not experienced before.
For me another negative was that the strings always seemed to be really prominent and my boyfriend could feel them during sex.
Overall a mixed experience - after years of hassle-free birth control I eventually changed to the POP due to the unpredictable bleeding I was getting with Mirena.