It looks awesome. It runs without firmware upgrade on the E-P5 (which I hope is the same as my E-PL5 that started shipping at the end of last year -- anyone Know?), has higher resolution, and has an eye-sensor to turn itself on when you bring it to your eye and off when you use the back panel LCD. At B&H it is priced about the same as the VF-2 was priced when that was the only option (and away from Christmas deal season). Older Olympus Pen cameras can run it with a firmware update, so it is certainly plug compatible with the VF-4. I presume Leica would not have had as good advance knowledge of it as the Olympus developers, but who knows?
scott
Update -- the E-P5 is not the same as the E-PL5. It has 5-axis (???) image stabilization like the O-MD, instead of what the E-PL5 uses (which works quite well), and the new VF-4 viewfinder. It should start shipping in the coming month. Same imaging chip and data path. 1/8000th max shutter speed, and claims improved autofocus. That may mean that it refreshes the EVF at 60 or even 120 fps, which would be very important, but less likely to have Leica support.