IMO, it does. But it's a tight squeeze.... with a few tradeoffs.
The main "negatives" (IMO) are huge files when they're not needed, minimal/negligible gains at higher "usable" ISO's.
The main positives are the ability to do things you can't w/ the D700 due to the huge files, dual cards, better performance at lower ISO's, 320 x-sync, faster AF. (and the quiet shutter is really nice too)
But if you're not going to make use of the positives, then they're not really "positives" are they?
So for most D700 users I see it as primarily a choice between costs/file size/ -vs- dual cards and low ISO performance (based on what *I think* is/should be considered important/relevant).
If costs (camera/file size) aren't a concern then the D810 is the obvious choice IMO. But there was a real opening here for the D750... they just screwed up the styling/design... again...