I never used them with my 5D3 as I only ever used the raw file, but I've started to use them now I've moved to a basic Fuji. I still shoot raw+jpg, but I find myself spending more time getting the shot right in camera now and using the jpg file more often than not. I've still got the raw if I need to tweak beyond boundaries, but having the camera give a reasonable representation on the review screen and in the viewfinder at the time of composing and then reviewing is helpful, particularly in B&W as it reveals the structure and texture of the image that isn't always obvious in colour.
I've ended up tweaking a number of presets around that - Yellow filter, Sharpness: +1, Highlight Tone: +1, Shadow Tone: +2, Noise Reduction: -2 for example is a common preset I've used as it gives me a more contrasty B&W image.