I have had the Paragard IUD for almost two years now. I have had a few problems with it but overall it's been a decent experience.
For the first few months I had continuous spotting. Invest in pantyliners. Cramps were pretty intense and lasted all month long not just during my cycle. My first few periods were a little rough with the cramping and extended time of my cycle. It probably took about four or five months for everything to clear up and return to normal.
I've had two major infections within the first year due to the IUD. Both caused extensive spotting and abdominal pain. My doctor wanted to pull the IUD but I begged and pleaded with him not to. Took a course of antibiotics that cleared it up pretty easily both times.
In spite of the problems, I am happy with the IUD. It took my body a long time to adjust to it but since then it's been fine with no problems. It's easier than the pill, patch, or shot. I had problems on all of them as well. Hope that helps. Good luck!