If there will be a time when I switch to using a mirrorless camera, here is one thing that I will definitely have to have: an electronic view finder with a diopter dial. Coming from a DSLR world, I find it so much easier to shoot when the camera is held up to my face. The act of holding it that way means I would have to hold the camera in a certain way that is stable. The camera would sit comfortable on my left hand while my arm is tucked into my side of my chest creating a stable platform for the camera for the not so fast exposures. Because I wear eyeglasses, it would be beneficial to have a diopter dial to adjust the eye focal length for when either I'm not wearing my eyeglasses or my eyeglasses becomes underprescribed. There is nothing worse than a blurry image in the viewfinder.
So, why a viewfinder anyway? For many case scenarios, it'd be fine to take photos with just the LCD but on a bright day, the LCD will look washed out. Have you ever tried to review a picture in bring sunlight? It's next to impossible to see anything. You'd have cup your hand over the LCD and even then it's not that easy. Also, having a viewfinder means more stability for fast action scenes when you can train your camera along the path of motion, being able to follow a subject with ease. Forget that if you hold the camera a foot away from your face. I think, for myself, my camera would be shaking too much to be able to track smoothly, and secondly, I can't look at things a foot from my place without removing my eyeglasses!
If you're buying a mirrorless camera, think of the EVF. It's a great feature!
