i think live view will be a great feature. there are just times when you don't/can't use the VF at all. when taking an overhead crowd shot with the camera held high, being able to see the shot on the lcd screen would work so much better than just taking a random shot.
Depending on what advantages vs. disadvantages I don't see why it couldn't be a possibility and a good thing for cameras. I guess it would just depend on what you could view live on the screen and what options you had. Plus I don't see it stopping anyone from buying that brand camera if they did it across thier line up. Did people stop buying Ferrari's when they started making thier cars paddel shifters instead of the traditional clutch and stick shift? No.
Live view is really for use on a tripod, not for hand holding a DSRL. The only time it might be helpful handheld is holding the camera overhead or at some other unusual location where you can not use the viewfinder, and that use often does not work too well because of brightness and angle of view of the screen. It will be quite a while before a video display can provide the quality of view that is needed to judge focus and framing in an action situation as well as a good SLR. Live view on a rear screen will never replace a viewfinder, but some day an electronic viewfinder may equal the current through the lens view. And Canon's current Live View does not support auto focus, limiting the usefulness of the mode to special situations. It may be technically possible to do autofocus off of the signal from the main sensor, but the current method of doing autofocus will not work without special sensors in the optical path.
By the way, you can try a video feed of the sensor into video viewing eyeglasses right now, because the video output of the 1DmkIII is live durring Live View mode. It is not a high resolution feed, but it could be played with for special applications. Holding the camera overhead in a crowd would be a good application to try it with, as long as you do not need autofocus at the same time. I do not have any video viewing eyeglasses, but have experimented some with a portable video display screen for a situation where I need remote viewing, but can not handle having a full computer to view with.
Everyone keeps mentioning it being hard to see the screen under so many conditions...didn't nikon say something about a 170 degree viewing angle and something to do with being able to see it in multiple lighting situations as well? hmm...seems like they're covering those bases.
I would love to see this post 5 years from now.... I suspect that they will both exist for a long time together, but eventually the optical VF would be replaced once the display technology get significally better. Many motivations for it including not needing a shutter mirror, a prism . Im not a pro, but as a hobbyists, I can see it disappearing from entry level cameras in 5-10 years.
