I bought a new F80 soon after they came out, and recently bought a used F100 advertised here. I kept the F80 because it's smaller and lighter and has a built-in flash (and it does have a spot meter). It's a great packing-around camera. The F100 is bigger, heavier, has faster and better autofocus and accepts all of the AIS lenses that I bought for my FM3A. I could easily get by with just the F100, but selling the F80 would be like selling my dog - in both cases we're used to each other. One other thing I really appreciate about the F100 is that it takes regular AA batteries, not those ridiculously expensive batteries the F80 uses.
The battery problem with the N80 can be solved with the optional battery pack. This lets it use 4 AA size batteries and it really doesn't feel too much heavier.
I have the N80 and F100. The advantage of the N80 is the light weight and pop up flash. The F100 is heavier, better built, and faster though. I paid full retail price (about $700.00 or $800.00) for it a couple of years ago because I thought it was going to be discontinued. I have only shot about 5 or 6 rolls of film with it. I stored it away not because I didn't like it but because the film labs in my area are pittifull. I also stored my F, FTN Photomic, F3HP, FM2N, S2 Rangefinder, and my Mamiya medium format equipment as well.
p.s. If you plan on purchasing a used F100, check the mechanism where the film canister goes (the little spool). I believe that older F100's had an issue with that part and were later replaced with a sturdier part.