Here is how I like to assign buttons on the D800:
Shutter: AE-L on half-press
FUNC: FV lock or spot metering
Preview: DOF preview
AF-On: AF-ON Only
AF-L/AE-L: Virtual horizon
Movie-record button: BKT
With exposure lock on half-press of the shutter, I can meter off a grey card or the back of my hand easily, the AF-On button only active decouples focus from the shutter button.
When I use CLS, I like to have flash value lock on the FUNC button so I can pre-fire the flash for the meter and avoid blinking eyes because of the preflash, otherwise a temporary spotmeter control is useful.
As I use fast lenses with a short DOF, I find the DOF preview valuable.
As there are other buttons that control the focus lock and exposure lock aspects, the AF-L/AE-L button is free to activate the virtual horizon.
As long as the firmware has been upgraded, the movie-record button can be reassigned to do something useful, like bracketing.
I don't remember where to change it, but the subcommand dial can be set to change the exposure compensation without pressing the +/- button in A or S mode. This carries over to the vertical grip.
The 50/1.8G is very precise in acquiring focus, but the old 50/1.8D is faster. I think it hunts less in low light than most zooms.
When it comes to the metering methods dial, the third position is for matrix metering. Matrix metering usually works well, but there is no warning when it guesses wrong about the type of scene and completely blows the exposure. I usually use centerweighted metering as it is very consistent.