I don't personally have one, but there is a wonderful little black capped conure at the rescue where I volunteer. She is very social and outgoing and loves to hang out with people. In general, I think their personality is pretty similar to green cheeks. Of course, just like any conure, they have the potential to be pretty noisy at times, although not as bad as a sun or nanday.
I wish I had more info to help you out, but hopefully someone else will come along and offer some more advice. I'm pretty sure IcyWolf has a black capped conure. Hopefully she'll read this thread.