We went through the combine factory a couple of yrs ago. It was well worth the while, especially if you're doing a "golden key" tour. Work close w/your dealer on setting that up. If you can spare an extra day, you'll also want to tour the planter factory & other JD exhibits/sites downtown. The employees interact well w/visitors. I'm sure that's part of their job descriptions. It makes feel welcome & not like you're intruding.

Take your camera & plenty of film! Or...batteries, I guess. They allow photos of anything/everything that I know of. It didn't always used to be that way however.