The weight without batteries according to Nikons website:
F100: 785 g
F6: 975 g
F5: 1210 g

The F6 has a very nice set of features, the matrix metering with AI lenses, the data printing between the frames, the build quality, the possibility to use a split field focus screen, the possibility to use it both with and without the battery grip, battery performance, data export with data reader MV-1, etc. all lives up to my highest expectations. I find that the metering system of the F6 matches my shooting style the best compared to my other cameras.
I have both a F100 and two F6s and the F100 haven't been used much since I got my first F6. The build quality of the F6 is in another league than the F100 in my opinion.
The battery grip MB-40 is very nice and gives outstanding battery performance with both rechargeable AA batteries and the EN-EL4 battery. When travelling I most of the time leave the battery grip at home and use the F6 with two CR123 batteries only. A fresh set of CR123, last about 10-14 rolls of 36 exposures.

The F6 is the best slr I ever used (including my Nikon D3) imo.