Mine was fairly painful to put in but that's because they had trouble finding my cervix (have a retroverted uterus - just means it points a different way) - it was like they mounted a search party in my vagina - torches pointing in all directions, 2 doctors fiddling about - after 5 minutes, I was going to volunteer to find it myself when ping, they caught sight of my cervix and in it went. I had cramps for around 3 days afterwards and then no more pain.
I was advised to have it for heavy periods - I bled constantly for around 6-8 weeks and had very sore boobs (quite a common initial side effect apparently). Since then I've had no bleeding but I can feel I'm about to get another period now. It's been OK - my skin has definitely deteriorated though but it is the most hassle free contraception I've ever had.