Kim, I like the 28-105 with my D700. Still very sharp with great contrast. I used it as my walk around lens on vacation and in that respect it was great. AF performance is pretty good for a non-AFS lens.
What I'd like to have is something a bit faster and quieter.
A question I have asked in the past when persons have asked about what to upgrade is this: What does your current equipment NOT do for you or NOT as well as you would like?
(Well, my answer, is that my flash isn't I-TTL and that's one thing I want to fix. I really need to take my own advice!)
Hearing all the grumbling in the D800 Forum, I'm especially glad I got a D700 when I did, and I don't have buyers remorse!