i just wanted to reply because i feel like there's definitely a lack of positive comments on IUDs on forums...!
i had a copper one put in a little over a week ago. insertion was painful but brief. afterwards i had moderate cramps for the remainder of the day. i spotted lightly for 4-5 days after insertion. by day 6 the cramps and spotting had stopped, and i had sex without problems (no pain, except for a certain position where my cervix was hit pretty hard, and partner didn't feel the strings despite them being left long).
every now and then i feel a slight discomfort somewhere in my belly, but that's just my body continuing to adjust to the iud, and i'm sure it will go away completely some time soon!
so, thus far, VERY happy with my IUD.