My primary camera is a Nikon D800. I use the AF-ON button for auto focus and the camera is always in AF-C focus mode. I use the AE-L/AF-L button for FV Lock (Flash Value for run and gun) and the Function Button for selecting non-CPU, manual focus lenses and for exposure lock. I've kept almost all of the lenses I bought from 1978 to date. I sold all those I bought from 1970 to 1976 as most were single coated. A camera like the D750 as good as it is lacks a dedicated AF-ON button so it's one button short and not the camera for me. I use shutter speeds above 1/4,000 and I'm spoiled by cameras with a 1/8,000. I still have my D300s and use it occasionally. The interface is almost the same as the D800 but the D800 is a bit better. I'd like a D4s image sensor and electronics in a D810 sized body, say a D810H.
I have a glut of 35mm film cameras. I wouldn't mind shooting a little ISO 400 B&W from time to time but my darkroom no longer has a sewer line. I'd also like to shoot a little 4x5 B&W. I can't see a day where I'll ever shoot color film again.
Anyway most of the time I'm using a D800.
Dave