The pain/discomfort of insertion is totally worth 5 years of not having to deal with BC. Just make sure you have someone drive you home afterwards...I was in no condition to drive immediately afterwards.
I had mine inserted in August. Never had a child. I have a high pain tolerance, and still - it HURT LIKE CRAZY. I won't sugar coat it, and I agree with PP - I was so glad I took DF (DH now) with me because there is no way I could have driven or survived public transport. For me, the cramps subsided within 2 hours, though. I also only had 2 ibprofuns, whereas a friend of mine (at a different clinic) received 4 small numbing injections. So definitely ask - apparently every doctor does it different.
My acne has improved (although I started using Proactiv at same time I got mirena, so hard to know what's what). For the first 3.5 months, I had a period every 28 days with almost a full week of spotting in between. Also, bad cramps around those times.
Now, I am in my 4th month and have not gotten my period (1 week late). Because there is that .001% chance, I POAS to be sure, but definitely not pregnant. So I think it is just my body leveling out and perhaps I will stop having periods, which of course was part of my hope with getting mirena in the first place.
Also - I have gained about 5lbs. Hard to tell if it is from mirena or from my post-wedding gluttoness food indulgences. So I'm going to buckle down after the holidays and if it comes off, I'll know it was the food. If not, I'll assume it's the mirena.
Having to take a pill everyday never bothered me and I never forgot it. Still, it is nice just not having to worry about BC at all.