Well, I don't have one now, but I've owned two F80's, and I would buy another in a minute. And if I could afford an F100, I would use the money to buy an F80 and use the change for something else (like a lens). The F80 is very much like an F100. It has a full, uncrippled user interface which is Nikon's current interface for its more professional cameras. You can choose and combine exposure and autofocus modes at your heart's content, or you can use it completely manually in every way. It has a polycarbonate body, but it's a very nice-feeling and visually-appealing shape and size, it has a nice viewfinder with super handy grid lines you can call up on demand, and its focussing ability, while not quite as good as an F100, is nevertheless very, very good. The body has quite a solid, brick-like dense feel to it. It's a camera that is truly a pleasure to work with, and it has pretty much anything anyone might ever need. I personally wouldn't use one in pouring rain without some kind of protection, but I wouldn't do that with an F100 either.
I would pick an F80 over a used F90 simply because it can use all the lenses that Nikon offers now and in the foreseeable future, and in my opinion, the user interface is far superior and more pleasant to work with. Manual focus lenses won't meter, but I've used plenty of cameras without a meter, so I don't consider that a big problem.