Horses for courses. There are clear plus points to the four thirds system but it's not the only answer, or (on evidence so far) even an adequate one when the criterion is low noise / high ISO performance.

Personally I think Olympus would do themselves and everyone else a favour by test marketing a 645 format digital body at a reasonably affordable price. Sure it would be huge and clunky by the standards of the E-xxx and there's probably no way it could be produced in the "bargain basement" price bracket, but two stops better noise performance than full frame is capable of is something which some of us would find valuable.