There are definite advantages of an EVF, though most of them have to do with things other than the actual view of what you are shooting.
The view through the OVF may be closer to reality and nicer, but you may see things which will NOT be in the result, for example when over/underexposing or you forgot to adjust the WB setting. So what's the point ? The result counts IMHO.
--
Photography is about subtracting from reality. We exclude subject matter by our framing and focal length choices. We can affect what details appear in bright or dark regions of the photo, or the tonal relationships of different parts of the photo, with our exposure. The more knowledgeable a photographer is the easier he or she can make those determinations. It is far easier, in my opinion, do to this when you see everything and can make those decisions while looking through the viewfinder. If the camera already is excluding certain information or items (such as detail in highlight or shadow areas) because the EVF lacks sufficient dynamic range, then it can make the photography process harder.
My idea of a good camera is one that does not get in the way of the photographic process. The more the camera gets in the way, the less usable it is and the more frustrating it becomes to use. There are many aspects of a camera's design that affect this "usability" issue, but for this thread all we are talking about is the EVF vs. a good OVF (at least that's what I'm talking about).
There are other aspects of an EVF, such as the information display, that can assist the photographer's decision making process. But, in my view, these are secondary to actually being able to see what is in the scene and not having to worry about whether cloud formations are blown out, or shadows are rendered as complete black, to name two examples. For some people, who don't shoot in conditions where the dynamic range of the EVF is a potential issue, this concern won't matter and the benefits of the EVF may hold sway. But for others of us, who do photograph in such conditions, the limited dynamic range of the EVF is a potentially serious problem.
Every time I think about this issue I think back to a photo I took during a trip to Antarctica in Jan 2009. It was late and the sun was going down. Clouds above the mountains were getting lit up, while in the heavily shadowed foreground there was a stream with king penguins. Unfortunately, I did not have with me my split ND filter (shame on me), and I had very little time to make the shot (the light did not last long). I had to frame the shot to get the cloud pattern I wanted while also retaining the foreground stream and penguins in the right location. If either the sky was blown out or the foreground area completely black, due to the limited dynamic range of the viewfinder, I would have had a great deal of trouble making that photo. Despite the lack of a split ND filter, I knew that shooting RAW I could push the exposure to the right, over-exposing the sky area while providing as much information as possible in the shadow areas. Later, in processing the RAW file, I adjusted the exposure in the sky area using various tools in Lightroom to bring back the detail (and color) while bringing up the shadows. It makes for a pretty nice 16x20 print. Could I have made the shot with an EVF camera? From everything I've seen and read about them thus far, not with the A33/55, and I don't know, but have my doubts, about the A77. This is but one example.
I just wish that when folks comment about this issue (EVF vs. OVF) they could step outside of their own perceptions and realize that there are other people who do all sorts of photography that they may not do. As I have said before, the EVF is fine for some people and what they like to shoot, and that's great. But it is not fine for other people and what they shoot. Whether or not the A77 narrows that gap enough remains to be seen (in person), but based on photographers whose opinions I tend to trust more, such as Michael Reichmann (Luminous Landscape), I have my doubts.
--
Mark Van Bergh
http://www.markvanbergh.com 
