I decided to do a test between the two cameras and lenses. I really wanted a small telephoto lens with my micro four-thirds setup, to replace hauling my Nikons for non-work related travel, but still have a usable lightweight kit if work related needs arise. I recently acquired the Panasonic 100-300mm OIS. So I decided to see how it stacked up to my other small telephoto lens, the Nikon 300mm f4 AFS! Both were shot jpeg, stopped down to f6.3, aperture priority, auto WB and auto ISO. These are my usual settings. While the D300S and 300mm is the superior handling combination, the G3, 100-300mm, 2 pancake primes, GF2 backup body, and spare battery/charger can fit in a smaller space than the D300S and 300mm (or 80-400 VR if you own one) while still being lighter and offering more reach. Here's my little test - Panasonic G3 & Nikon D300S 300 f4 AFS: D300S/300mm @ 300mm (approx. 500mm full frame): G3/100-300mm @ 250mm (approx. 500mm full frame): D300S Crop: G3 Crop: D300S Bigger Crop: G3 Bigger Crop: Overall, the D300S & 300 handles better, but I think the G3 & 100-300 holds up pretty well in good light and despite lacking the faster AF and handling, the weight savings are worth it. Comments welcomed!