yes I had the copper one and I didn't experience much worse pain and cramping so that wasn't a problem. HOWEVER around that time I started losing a bunch of hair and have had scanty periods ever since. I also got flu like symptoms on the first day of my period every time. I can't remember exactly how long I had it in for, but I suspect it may have been the cause of some of my problems. I can't pinpoint it exactly. If it wasn't the cause of those things I think it would have been a fabulous device. But, like I say, I can't tell. So guess it depends on whether you want to risk it.
If there's anyone out there who's looking for a natural birth control method go to http://www.naturalmethods.com
-- the device may seem crazy but I have been using it for two years and have not fallen pregnant. I fell pregnant within three weeks of coming off the pill so its not like I have difficulty conceiving.