Hello,
I had mine for 5 years and it was the best thing I ever did.
Having it fitted was quite uncomfortable (about a 4/10 on the pain scale) and bled intermittently for about 3 weeks afterwards.
Since then, no periods at all, no mood swings, no weight gain, nada...
I had it removed as DH and I are now TTC and even the removal was straightforward. I have been monitoring my cycle with a Clearblue Fertility Monitor since having it removed and had a 'normal' cycle immediately.
The only thing I could find to complain about (if I look really hard for something) is that I had terrible PMT this cycle, as I have got so used to not having any hormonal mood swings at all - DH was quite taken aback by my tearfulness and general unreasonableness in the few days before AF arrived.
I guess this is normal, but kind of took us both a bit by surprise as I had the Mirena when we first met so he had never seen me hormonal before - I have advised him to dig out his hard hat once I fall pg!
Overall though, I can't recommend it (Mirena) highly enough! I will certainly be having another one fitted after having a DC (fingers crossed!)