Those buttons that can be configured are truly valuable real estate. You can set the 3 buttons up by hitting the INFO button on the camera back twice. This gives you a menu.
But you would rarely need to configure Virtual Horizon that fast. Why not save the button and make Virtual Horizon one of the options on MY MENU? You can navigate there pretty quick and get Virtual Horizon working. Or, you can set it and leave it on all the time.
I have GRID set most of the time and don't worry about it.
On the D7000 i wasn't a big fan of the Virtual Horizon in the view finder. If i remember correctly you'd have to configure the FN button to turn it on... then you'd have to press-and-hold the FN button and the exposure info in the viewfinder would be replaced with the 'virtual horizon'.
On the D7100 it works WAY better... Press the FN button (or whatever button you have configured) and the Vert. Horizon stays on the screen until you turn it off. Its also been moved off the exposure area and onto the actual display.
Still doesn't make my horizons straight during high action shots.. but at least i cant blame the camera now
>Has anyone set the function button to virtual horizon? >Does not do anything for me?
If you are using the viewfinder for framing and want a quick, simple, and efficient method for "horizontal leveling" the "Viewfinder Virtual Horizon" (page 231 in the D7000 manual) is nice. I always use it with my D7000 and tripod/ball head because the leveling bubble is hard to see when the camera is at a standing eye height and also many times while hand holding too.
I have assigned the "Horizontal Virtual Horizon" to my depth-of-field button (page 230 in the D7000 manual) and it works great. Press and release the DOF button, horizontally level the camera while framing the picture through the viewfinder, press and release the DOF button again (it disappears) and your done.