Either it's due to a pre-production unit or there is something wrong with some units. Coming from the EM-5 and NEX-6, there is no noticeable difference for me between EM-5 and GX7 in switching between the LCD and viewfinder. I still have all three cameras and can compare them side by side. The NEX-6 is slightly faster than both. In all 3 units, its not an issue at all for me when shooting.
The EM-5 implementation of auto switching also has a big problem for me. Because I'm long sighted and don't wear glasses when I shoot, I depend on the EVF with it's diopter correction to review just taken photos for sharpness. If you want to use the EM-5 EVF to review, you have to turn off auto switching, which is a PITA. Fortunately, the GX7 works exactly like the NEX-6 and other mirrorless cameras. To review in playback mode, I just lift the camera to my eye. This is one of the ergonomic issues that has been bothering me for the last 2 years with the EM-5. If it's still in the EM-1 and future OMDs, I will have to think hard before getting one again.