I have a Mirena IUD and LOVE IT. It is by far the best birth control we've ever used. I had it put in almost a year ago, and I had minor spotting during my period times for about 3 months, then nothing since.
My insurance wouldn't cover the pill, and our boys were only 4 and 1 so we just didn't want to get pregnant yet, so I called our insurance to discuss options, and she told me that an IUD was covered 100%, I just had to pay the copay of $15. The actual cost of the IUD, according to the paperwork I got from the insurance company, was $525, plus the cost of the insertion which was $218.
CAll your insurance company and see what they cover, most will cover the IUD now at whatever % the rest of your coverage is, like 80/20, or 90/10, or you pay a fraction of the cost, insurance picks up the rest.
I would highly recommend an IUD to anyone looking for birth control for more than a year. I know that if we end up having another baby I'll probalby get an IUD again, unless my husband decides on a vasectomy! :)
Good luck on your decision.