The speeds should be very similar between the cameras. The D100 specs at 3 fps max and the F/N80 at 2.5, but the D100 has the shot buffer limit of 3 frames raw, 6 frames jpeg.
As noted, the flash mode and flash exposure compensation buttons are in opposite spots for the two cameras (inexplicably)
The D100 has the multi/single sensor selector on the mode dial, the F/N80 has a seperate control next to the 4-way rocker pad
1/3 stop metering for the D100 vs. 1/2 stop for the F/N80
1/180 flash sync D100 vs. 1/125 F/N80
D100 has a flash GN of 36, F/N80 GN 39
D100 won't TTL meter with anything but DX Speedlights, F/N80 will TTL meter with any Nikon TTL Speedlight, including DX models
Both cameras use the same CAM 900 AF module
They have the same metering EV range
They have the same eyepiece and grid overlay display
Similar plastic composite body construction
If you want the most seamless transition from an F/N80, the Fuji S2 has identical controls including a functional multiple exposure control. The multi/single AF point selection is done via one of the function button actions on the camera back. Speedlight TTL compatibility is the same.
I don't think it would take long to become accustomed to moving between the F/N80 and the D100.