i don't have one, but i've inserted about 15 -which doesn't sound like many, until you compare that # to the less than 5 'old-style' iud's i've done.
most patients loved them. localized effects, and of course progesterone only, so none of the weight-gain or bloating or headache or blood clot issues some have with pills. for most, they had some spotting - like needed a panty liner - for a month or so, then basically no periods. however, that's not guaranteed. there are certainly people who had a 'normal' period amount for a long time before settling out, and some folks continue to have fairly normal periods with a mirena.
if you haven't been on a progesterone-only type birth control (like depo provera, 'the shot', or the progesterone-only 'mini-pill'), consider having a round of the shot to see how it affects you. easier to back out at that point if you don't like it. i wouldn't suggest trying the same with the mini-pill (which you take every day like the combination pill), because that is very time sensitive & if you're off by a few hours, you can start bleeding.
mirena is extremely effective, though i have to say i had someone get pregnant on one.
bless her heart, she worked in the office & is just sooo fertile. but, hey, we all know stories of people who got pregnant after tubals, too! when they say 99% effective, *someone* is that 1%...
if you decide to get one, take 800mg of motrin (if you can use motrin) or 220mg of naprosyn (ditto) to ward off cramps from insertion. that's what most people complain about - not the insertion itself, which is basically like a long pap smear, but some crampiness afterwards.
feel free to pm me if you can think of other questions!