Ben,
Sorry, I didn't see that you included the 50 Macro, but that lens is almost 1.5 stops slower than the Panasonic pancake, and almost 0.5 stops slower than the Zuiko 50mm f/2.0 macro, partly killing off some of the high ISO advantage of the 5D.
There are things to be said for both options, and a fast lens and high ISO is often useful. The fast lens is already on the Panasonic roadmap, while we have to see what the high ISO is like. It will probably not be as nice as on a 5D or a D700, but on the other hand, I regularly sell images taken with my old E-1 at ISO 800. As for resolution, 12MP mostly does it for me, and the distance up to the 5D isn't very long for any practical use. What the new 5D will bring, remains to be seen.
Here's an example taken with the E-1 at ISO 800, notorious for grainy high ISO, hand-held at 11mm and 1/13s, which was only possible because of the low level of in-camera vibrations, partly due to the small mirror/shutter. The M4/3 cameras obviously have no problems with vibrations, since they have neither mirror nor shutter:
There are other sides to this that are highly individual. Mostly, when I'm out and about, I want a camera that looks small and "amateurish". It looks less pretentious, and it's easier to approach people without giving them the feeling that they will end up on the front-page of Time Magazine. The articulated LCD (and no shutter sound) also makes it possible to take photos from difficult angles and/or without being noticed.
A few fast primes from Olympus will be important to make this system sing, and I'm quite sure they will deliver. A macro is obvious, and a fast 100mm would be nice. Maybe the 100mm f/2.0 macro that has long been indicated on the Zuiko roadmap will materialise in M4/3 form. That would be nice