All but two of my lenses are manual focus lenses - do you mean that you use live-view tripod mounted or hand-held ?
Because I never quite understood why anybody would use live-view handheld - isn't it just too slow? I have the precision screen installed and its enough for me.
Both. It is slow (or "deliberate" if you prefer) for handheld work, but since most of my subjects are of the stationary variety, this is not an issue for me.
I have the precision screen installed as well and I use it when I need to work a little faster or when shooting stopped down, but I frequently shoot wide open and/or up close, so there is no substitute for the pinpoint accuracy you get with magnified live view.