I've seen a couple of plugins that deal with custom fields, and in theory they sound like they work just fine. What I would like to do is a bit more custom than that...I think.
I want to add my own form so my Users can pick which county they live in, then have that write to my own datatable. That's my primary issue. I know how deal with getting the form to write to a database. I don't seem to know how to get it on my registration page. Side note, it's not something they necessarily need to change, so putting it on their profile isn't necessary.
My secondary issue is to have them be joined to a User Group based on which county they live in, but that's another day.