So another reason people use DSLRs is because the presentation of the scene to the user is optical, and therefore you don't have the shutter lag associated with the use of the LCD for framing.
I'm going to suggest that we use an acronym for mirrorless cameras like the E-PL1 with interchangeable lenses: EVIL, for Electronic Viewfinder, Interchangeable Lens. Personally, I believe that EVIL cameras belong in the dSLR forum, because most posts are about lenses and ports, not viewfinders. I agree that the viewfinder issues are different between EVIL cameras and SLR cameras.
I do not agree about the LCD lag on the E-P1. I can wave my hand in front of my E-P1, and not see a difference between the movements of my hand and the movement on the LCD screen. Modern electronics are FAST, and pushing a few electrons around an LCD screen doesn't take a whole lot of time. As for shutter lag, I have a Nikon D90 that I can compare to my E-P1. Using manual focus, I don't see a difference in shutter lag between the two bodies (using live view on the E-P1 and the viewfinder on the D90). I'm sure I could come up with an experiment to measure the shutter lag with falling pieces of wood and simultaneous triggers to measure a few milliseconds difference in a lab, but that isn't going to matter in the field. This only applies when using manual focus, though; the E-P1 has truly AWFUL focus lag, which is probably where most of the online complaints come from.
I don't mind the focus lag on the E-P1 because I shoot mostly in manual focus. My underwater images are even more likely to be manual focus, because I don't trust autofocus for macro images (too many shots ruined because the camera decided to focus on the coral instead of the blenny) and I don't need autofocus with the depth of field of fisheye or wideangle images. I spend enough time setting up the aperture, shutter speed, strobe position, strobe power, etc. that adding manual focus isn't much added work, and it's better than repeating shots because the autofocus did something silly.