Yes, for exposure. We have always been able to see blowouts in review mode, and it was added to Live View on DSLRs for video so you could see it in real time. With mirrorless since the EVF is reading off the sensor it makes sense that it could be made available in it, but I guess we're not there yet. I shoot a lot against gray skies and to be able to see in the viewfinder when those skies are unrecoverable would be great. Same thing when a bright blue sky has blown out highlights in clouds. When shooting landscapes you can always check the histogram and reshoot, but when tracking a bird it would be great to know I need to ramp down the EV value.