I too went from a 35mm F100 to the "digital version" D700 four years ago. While I was originally thinking of waiting at that time for the next generation "D800" (which it ultimately became), I am glad that I got the D700. At minimum, it afforded me a whole new world of photography and has travelled extensively with me over the years.
The feel of the F100 is awesome, especially when mated with my MB-15 (?) grip. I haven't purchased the D700 grip as of yet (considering it though), but find it a nice camera in terms of ergonomics, even without the added piece.
The D800 appears smaller and maybe not as nice to hold, but I appreciate that this depends on the size of one's hands, etc.
When it was first announced, I too felt a bit torn. Sure, the image quality is potentially much better, but as has been discussed, is really beneficial when one outputs large prints. I don't do that, so it is of little benefit. I know there are many other pluses, but in terms of shooting, the image quality, and what I use my photos for, it is of no consequence.
Just like when I'm shooting slides on the F100, I look at the D700 the same way. The output is great and it is so versatile.
I'm looking forward to my next vacations where I can enjoy it further.
As others have stated -- it is a true classic that is still very competitive today.