Hi,
OVF means mostly SLR technique and that means a shutter release lag. With OVF the shutter release lag can be very short, say 20 ms, but the viewfinder image may also have a significant lag.
The odds may be that you won't shoot birds in flight or fast, unpredictable action like say ice hockey with an MF DSLR.
One thing I have sort of noticed that folks who use EVF regularly sort of prefer it. It can be set up as What You See is What You Get. For me personally the magnified live is the essential parameter. OVF has some problems in bright conditions, but a good rubber eyecup helps a lot and I prefer to work with an eyecup on DSLRs, too. In the dark an OVF can be magnificent.
EVFs can drop the mirror box and can therefore offer a short flange distance, that makes the camera compatible with view cameras like the Cambo Actus or in my case the pocket size tilt and shift adapter called HCam Master TS II.
This is not saying that EVF is preferable to OVF, but EVF is an enabling technology in many senses.
Best regards
Erik
This should be the case on all digital touch screens now. Apple still owns the patent on using you fingers in a pinching movement to zoom in and out.
Insofar as my gripes about the system, I have the same two I have with all mirrorless cameras, the EVF lag and its poor performance in high contrast or low light situations. This is a camera made for handheld use, and to have a lag in the view finder is unacceptable. High contrast scenes make highlights and shadows in the VF too bright and too dark with little mid tones, and possibly way too much noise in lower light situations.
I will continue with my OVFs for now, although I would love the lower weight.