well I don't see why focusing speed and accuracy would be affected? I think there is a few ms of lag in the display though. Im guessing battery life will be affected by having even a small lcd in the eye piece on all the time.

You can look at it like its a p+s, with changeable lenses and proper manual modes.
Or you can look at it like its a DSLR with no prism and half the weight.

But I can see all cameras heading this way because to remove a shutter curtain is going to mean massive reduction in camera shake. And as long as there is no perceptible difference with the live view finder to a normal one no one will care.

They probably add features like digital zooming on the view finder so manual focus accuracy would be even better.