Paul,
They're apparently enhancing the eye and face lock performance. Agree it's pretty good now, and frankly excellent for the kind of photography you and I do, but Sony kicked their butt in a head-to-head comp of moving people, so I think Nikon took it sort of personally
More though I think, will be the CF-Express compatibility in that same update. The CF-e cards are here now, and performing faster at lower cost than XQD. Also, I believe they're putting the raw video FW in as well -- I don't shoot video, but that's apparently a big deal for the serious video folks.