I was more conservative - E-M5 MkII to E-M1 MkII - so the heft and and the grip are complete difference to slim M5 profile. But it handles the 40-150 Pro much more convincingly and the AF performance is hugely advanced, as well as the battery life. I can hand hold to 1 second OK. The Hi Res image is definitely superior. But all said and done - it is a different beast so I think it is possible to justify owning both for their differences!