Well, I was really hoping that Nikon was going to surprise me with a D4 sensor in a D810 compact pro body, but as I mentioned before in my Nikon Df review Nikon would never do that again. Basically Nikon got everyone all psyched up for the D750, which sounded like the D700 replacement and let us down with what is basically a D620.
Don't get me wrong, there are a lot of really good upgrades such as a tilt-screen, better video, the amazing D4s 51-point AF system, highlight-weighted metering, Expeed 4, power aperture in Live View and more, but they jammed it into a consumer body with a non-pro build and an awkward layout (if you're used to the pro bodies). If you're advancing up through the D7000-D600 series cameras you're going to be right at home, so for many folks this body will be great as an upgrade camera or as a complementary camera to a D600/610.
For those of us who are really used to the D700/D800 style bodies this was a pretty big miss from Nikon. Things we're missing on a real D700 replacement are dedicated ISO/QUAL/WB/BKT top mounted buttons, a full magnesium alloy body, a body that's a little larger for a nice solid grip that doesn't cramp your hands when shooting for extended periods. A mode button that only has PSAM and none of the scene and effects modes that most pros and advanced shooters find unnecessary. And very importantly a camera that was killer in low light with a fast frame rate of 8fps or better.
Looking at the D750 as a whole it's a really great camera, but the D750 is what the D600 should have been in the first place. And after all of the D600 issues and the quick "upgrade" to D610 I think Nikon is simply trying to bury the stigma of the D600 moniker by laying it to rest and trying to associate it with one of their best cameras, the D700.
It looks like there will be no lightweight alternative to the D4s, but I knew that all along, but didn't want to believe it.
We're still an hour away from the official release, but photos and an official Nikon video have been leaked already. Check 'em out below.
Edit: Official specs have leaked as well:
The Nikon D750 from Andrew Reid on Vimeo.