Our Nikon F4s was purchased by Lea at a university surplus store for an amazingly low $35. It's an enormous and incredibly powerful camera, and everyone who's interested in film photography should try and get their hands on an F4 at some point. Our model bears the “s” suffix because it has a vertical grip attached that allows for extra batteries which power the high speed drive motor. Overall it takes 6 AA batteries and can fire at about 6 frames per second (when in high speed mode) - meaning that if you were to hold down the shutter button, you could use up the entire roll of film in just a few seconds; provided each exposure was like 1/250 and there's no AF delay.
The F4s offers much of the digital precision that the F80 offers, but in a very different way. The F80 has an LCD display and easy to use dials; the F4s has a myriad of levers and knobs and buttons. When we first got it, we were entirely unable to turn it on, open the back, or even take a picture. The F4 certainly has an incredibly steep learning curve. Once mastered, however, it is an amazing camera and one can clearly see how it would have cost $2,500 when it was new in the late 80s. Using the F4s is akin to driving a similarly aged muscle car. Useless unless you know what you're doing and maintain it.
Main con? The F4s is heavy. Not only does it take 6 AAs, it is entirely made of very dense metal. The body alone weighs about a pound and a half, and then you have to add a lens on top of that. If you don't mind the weight or the steep learning curve, it's an incredible camera with many fantastic features.