I really hope that the new 100-300mm is both sharp and fast focusing.
The 45-200mm lens put me off m4/3 completely.
I used it with a G1 at the Miramar Airshow and the soft images , slow focus and vignetting at the 200mm end left me disillusioned.
Subsequently I found it performed better on the GF-1* but by then I'd moved on again to APS-C and enjoyed the extra quality.
Still got the G1 and GF-1 with 20mm , 14-45mm and 45-200mm but they seldom get used.
Could the 100-300mm be the lens to get me back? I hope so but the samples on the Lumix website look rather soft to me.
I also have the 45-200 and focus is realy slow, in low lights it is even not focussing sometimes.
Although I will have use for this lens, indeed for sports or fast moving objects it is not a good deal! I wonder if the 100-300 will be that faster since the camera only uses contrast auto focus. Looking at the prices I would expect some improvement in IQ and focus.
Still I think your DSLR will be better performing. But the GF1 with the 20mm is something to hold on to!!
Check out the 45-200 thread. The lens is actually very good and I love mine. It is clear from the pictures others have taken with the 45-200, that it is a terrific lens in the right hands. As to the future of M4/3, my feeling is that it is the future. My Nikon DSLR and lenses are in the closet and will probably stay there. The more time you spend with M4/3, the better you get at exploiting its advantages.
I'm very tempted by this 100-300mm... my mirror lenses are fun and all but when it comes to shooting moving subjects there is no way I can manual focus accurately enough to get decent shots. I saw it for £449, not bad at all. I guess it's still not enough to do serious nature photography, but a step forward nonetheless, and probably the best one can do now with a native micro4/3 lens. I wonder if I should sell my 45-200mm if I get this one, just to feel less guilty about it!