M 4/3 has now been around 10 years.  Used by Olympus, Panasonic (Lumix, and Leica pinched the innards of some), and Blackmagic film cameras. A review of what's good and not so good (like any format).
(I like the Olympus Pen-F and Leica D-Lux 109 as they have the dedicated plus / minus exposure compensation dial.)
https://www.youtube.com/watch?v=m072i-jDSg4