The Nikon Straps that came with my D3S are very good... I use them all the time. ( I'm uncertain if this is the same as the D700 grade ?? )
Anyways I like the Thinktank Straps also - very strong and stay on the shoulder.
Ohh, I not very sure too whether the D700 strap is as strong too. Prefer sling to neck strap cos less straining. Will check out the few brands mentioned, thanks!