[joachim]

I have read that the simplest way to try and measure it is using a high speed camera, like some of the high speed Casio compact digitals, and video the view finder/LCD and the "scene" at the same time, and record a flash of light. 

I also have read that the lag increases with lower light conditions, because they try to keep the EVF feed "clean".

Thanks. You know a website that publishes the results of this?