I'm half-way down this page, and my wife is on my back to stop wasting time and start helping around the house:
Nikon N90s, N90, F90 and F90x.
I'm very curious about the F100, as Rockwell says it eclipsed the N90 (the F90 is just the Canadian name, like a YJ vs. a Wrangler), but I read somewhere on this site where someone put down the F100. I can't remember why.
I'm all for having an F4 and a lesser camera as a back up. I think the N90 is a great camera, from everything I've read, but I need to finish that page and then read about the F100.
I like my FE2, but I hope to upgrade to these better cameras this year or next.
For you, Joe, it comes down to if you want AF or M operation. If you're not after AF, the FE2 is a great choice. For AF the F4 is possibly the best choice, followed by the F100 or N90.
A purist (me) will always choose the F4 over the F5.