Panasonic 100-300 or ......?

Did you see the review of GH3/100-300 used for safari by a pro? http://www.naturalexposures.com/corkboard/testing-panasonics-newest-micro-four-thirds-camera-the-gh3/

I think that will give you a balanced view as to what the performance really is of m4/3 at the moment.

He does seem to have a follow up that says he might have run into shutter shock with one specific picture taken in low light: http://www.naturalexposures.com/corkboard/update-shooting-the-panasonic-gh3/ -- from comments I have read elsewhere, that is an issue you could easily run into with cheaper dSLRs as well, it is not something only found in m4/3.

I went on safari with a GH2 and 100-300, kept shutter speed high most of the time and I am very happy with the results.

Niels