[Seymour]

Mirrorless cameras do not suffer from front or back focus.

Thanks for clearing that up!

Another reason never to go back to mirrors.
 

When using EF lenses via e.g. Metabones, focus might be painfully slow on a mirror less, depending on a number of factors.

I am putting a lot of stock into the 2.0 firmware for the A7 II. There are very enthusiastic reports. I was going to delay the full format purchase until next summer or so and get a small MFT system for now, but since Sony improved the co-operation with adapted lenses and definitely addressed the main issue (RAW compression)... why wait?