FernandoBatista on mu-43.com has posted several amazingly sharp bird photos, all shot with the new Lumix DMC-G5. Some were shot with the Lumix 100-300mm f4-5.6, others with an apochromatic telescope adapted to the Lumix body.
(Click Here) to see them all.
I have really gotten some nice images with the 100-300mm Lumix lens. Sitting birds are one thing. Shooting them in flight, which really helps to make them look less like stuffed taxidermy models, is much harder. The Lumix lens' fast autofocus is pretty good, but it's definitely still not a high hit-rate endeavor.
This is about the best I've done on birds in flight with the Lumix 100-300:
I have this one enlarged to 12x18 on my wall, and the sharpness is remarkable. It's easy to tell these guys aren't stuffed!