I believe it will work in A mode for some AF bodies such as F801, as I used to use my F801s with AI and AIS lenses in A mode.
I guess the key is, does F80/100 come with the mecahnical coupling ring around the lens mount to detect the setting of the aperture ring on the lens? If it does then it will work in A mode for AI/AIS lenses, otherwise it can only work in M mode.
Anyway I think 85mm focal length is a good focal length for portraits, even though I personally prefer slightly longer focal length (>105mm). That's why the AF 85mm f/1.8 worked very well for me on a DSLR, due to the cropping factor.
It has nothing to do with the metering system. The F100 and equivalent or higher Nikon bodies (F5, D1, D1X, D2H as well as some older AF cameras) has a little tab around the ring mount to allow AI/AIS lenses to communicate the aperture to the camera body. New lens do not need to use this tab (indeed look at the new series of G, DX lenses which don't come with an aperture ring).
This physical difference is the only thing standing between metering with an older lens on your camera or not. Of course, you can always have your AI/AIS lenses chipped...