I bled FOREVER after Devon! A couple of months, at least! I remember going to my 8 week appointment and warned my doc that I was still bleeding and for him to be careful while meandering 'down there'! LoL! He reassured me that it's normal for some women to bleed for a long time afterwards.
I got the IUD at about 3 months post-partum. I hated it. I got it just a few weeks after I stopped bleeding, and it just made me bleed again! Most people I know who have it love it! My doctor told me that I would bleed and have cramps for a day or two, and then it would stop. Well, my cramps stopped (although they did reoccur every couple of weeks) but the bleeding never stopped. I had it removed in February after almost 3 months of non-stop bleeding.
I loved how convenient it was, though! It sure was a nice method. I just hated the bleeding and was using a tampon every day, which I know wasn't the safest thing!

I went on Yaz, instead. I like it. According to my doctor, the IUD is 100% effective when it's in. (Meaning that so far there haven't been any pregnancies while the IUD is in.) However, it can fall out and some women don't notice it. That is where it has become less than 100% effective, when a woman gets pregnant because it falls out and she doesn't realize it.
Anyway, if you want it, I say go for it! There are almost no "oops" with Mirena and it's so convenient!