Well I got the the first unit from Nikon this week and after building a some-what usable rig I put it to the test chasing my daughter around the farm for an hour. A couple of quick notes:

1) The Flat profile is ok but nowhere near s-log/c-log for DR
2) The record button is in a terrible spot once you add a cage/handles to the rig- requiring you to reach right around to the front of the camera.
3) The files straight from the camera look nice but fall apart quickly when grading. This is a particular nuisance because:
4) 100/120p is internal only (no HDMI) so a lot of my b-roll is going to have to be shot in 8-bit 4:2:0 h.264.
5) HDMI sucks. I want my sturdy, locking BNC cables back!
6) 1080p quality is miles ahead of the 5DmkIII which was my last experience with DSLR video.
7) Muscle memory is going to be harder than I though to overcome with regards to focusing (and we're contractually locked into using Nikon glass only).
8) The battery indicator seems to only be displayed on the top info screen, not the main LCD - at least until the battery flashes red just before it dies. Makes it hard to continually check your battery level.

I'll add more thorough notes once I've done some more test shoots.