I had my mirena for a year and a half but I wasn't too happy with it. I recently had it taken out. I thought I would love a birth control that I didn't have to think about or worry about -- but I did think about it, more often than not, and a few things made me worry.
I had mine inserted at my 6 wk pp check up, too. My lochia had stopped and I was finally feeling better. After getting it inserted, I started bleeding again and it didn't stop for 5-6 weeks. Ugh, it was a nightmare. And it was painful for the first few days - I remember feeling like absolute crap.
Then when all that finally went away, the strings had to be cut. They were poking me, poking DH when we DTD, and were just overall annoying. So, I had to go back to my midwife and have the strings cut. Not painful, not horrible, just annoying.
After THAT was resolved, I noticed how low my libido was. DH would literally have to beg and plead and I was just so not interested. I'm not going to say it was 100% mirena's fault, b/c having an infant can also deflate your sex drive, but it was a bit ridiculous.
Then (and I guess this was the big one for me) I learned that fertilization can still occur, but it won't implant. It bugged me. A lot. I tried to put it out of my mind, I tried not to think about it, but at the end of the day I felt like I didn't want to DTD during potential "fertile times" and was distraught over it. So I talked it over w/DH and he agreed that we should just go back to FAM and condoms.
So just think about it. If you can get past a few roadblocks, you should be fine. I'm just amazed at how different I feel w/o it (libido is back, fwiw) and I just feel more comfortable using FAM and condoms for now.