This video demonstrates the difference between the multi aspect ratio sensor of the GH2 and the non multi aspect ratio sensor of the new GH3. It also shows how important the additional dynamic range of the GH3 could be. So how important is the M.A.R to you?
http://www.youtube.com/watch?v=zFnY5tlvW8M
http://www.youtube.com/watch?v=zFnY5tlvW8M