I have a good SLR, and looking through an electronic viewfinder is so poor in comparison (even on an expensive pro-sumer model) it's hard to describe. Our visual system can cope with such a huge dynamic range that it makes little sense to neuter this ability while shooting.<p>An SLR is able to capture RAW data, which can be mapped to different jpeg/whatever images, so there's a big disadvantage in looking at a specific instance through the viewfinder.<p>In common situations the preview and default jpeg output is absolutely fine, but when you get to more challenging lighting you need to trust your eyes at the time, and the awesomeness of RAW later.