I had one. I think that they are a wonderful idea, and everyone ttc or ttc soon should get one as well.
Personally, I scheduled mine at the same time as my yearly (two birds with one stone) So, they did my pap and everything the same day. Basically, they checked my blood pressure (I have high blood pressure, they wanted to make sure it was under control), she went over all the medications I am currently taking and we discussed which one's I should be off before I get pregnant, once I get my positive, and which one's were safe for pregnancy. She also went over my 'lifestyle' asking how much I drank alcohol, caffeine ect. And went over my exercise routine (or lack there of) and what was suggested for now and in pregnancy.
She then sent me for blood work to check that I had all of the correct antibodies from chicken pox and...reubella (?). That way I could get the vaccines if I didn't have the correct antibodies, before I become pregnant.
That was pretty much it. She prescribed me some prenatals and I was on my way!