While I can't speak for the Sony cameras, I do (also) extensively use a M4/3, with the primes I've had for years/decades.
First, the existing M4/3 cameras use a different and more accurate (albeit somewhat slower) AF method than the vast majority of (D)SLRs. In fact, in the test I previously mentioned, a M4/3 camera had the most accurate focusing results of all the cameras tested.
That said, manual focusing on my M4/3 viewfinder (not rear LCD) doesn't even come close to manual focusing with a *good* optical viewfinder/screen combination. Better than expected, yes, but the majority of my film cameras will reliably focus more accurately.