I have both the 105mm f/2.5 and the 105mm f/4 Micro-Nikkor. Both excellent lenses, but the f/2.5 lens is a better lens for portraiture for me. There's a smoothness in the transition from sharp focus to out-of-focus areas that the Micro-Nikkor doesn't match. It's hard to describe the effect, but it's definately there. The Micro-Nikkor is an amazing lens at macro distances, but it just seems too harsh to me for portraits.
I used to have the 85mm f/1.8, but I found that I reached for it so rarely that I got rid of it. It's a wonderful lens, especially in available light situations, but it never matched the way I envisioned my work...the longer reach of the 105mm works better for me.
Oddly enough, the 140mm macro is my favorite portrait lens on the Mamiya RB-67. I seem to go for shorter lenses as I use larger film. I'm not sure why that is...probably a sign of brain damage from my mis-spent youth.
One thing that I believe it is safe to assume: Nikkon makes the best range of high quality lenses in the traditional portrait focal lengths. I don't believe there's a real dog in the bunch.