My husband doesn't feel it at all, not even the string, and neither do I. I even have a tilted uterus and I still don't have any problems with it. The string feels a bit like the plastic thing that holds the tags on the clothes at the store at first, but you don't even notice it and it softens up very quickly. I only know what it feels like because I asked them to let me feel it before it was put in so I could tell my hubby what he was supposed to be checking for (he checks once a month after my period to make sure that the string is still there).
Personally I always felt like I was poisoning myself when I was on hormonal birth control (probably because I always responded so negatively to it), so I chose the ParaGard. I'm very happy with my decision and haven't regretted it in the three years I've had it. It has been very effective (and we've put it through it's paces for sure!). It did cause some heavier bleeding for about the first 6 months until my body adjusted to it, but to me that was a small price to pay for non-hormonal, set and forget birth control that's good for 10 years!
I do know that some women have experienced problems with IUD's, but I never have so I can't go into details about that. Just make sure that you know the risks vs. the benefits of any method of bc before you take it.