Another item to consider is that the Olympus Zuiko Digital lens was designed totaly for the 4/3 system as so the clarity of the images are going to be that much better.
Besides, The high end Glass and Coatings on the Pro lenses are putting Canon to shame in sharpness.
If you think about it, both Nikon and Canon are trying to use conventional lens design into a digital format. Yes both Nikon and Canon have high end digital lenses, but the price of these lenses are exactly on par with the Olympus Glass.
You end up gaining with the Olympus system in the end.