Like most of us, I haven't seen a GH3 to comment. The G5 is a nice camera, but I'm not sure it's any better than the GH2 for stills. The GH2 has the multi-aspect sensor (sort of a weird way of using sensor real estate), and is $20 cheaper than the G5 at Amazon. (And half the price of the GH3, but you knew that already.) I've been using the GH2 for almost a year, with the Panny 14 and 20 and the Olympus 45 -- good combo for candids and low light. I'm very happy with image quality up to ISO 1600, and have made good prints at 3200 and 6400. The 25/1.4 and the 12-35 are on my short list, but the 20 and the 45 are a great combo.
In general I think it's better to spend the big money on lenses rather than cameras. The investment lasts a lot longer. That's why I'm always a little behind - I wait until the latest-and-greatest camera is near the end of its life span, then buy it. Heck, I'm just about ready to get another GH2 and take advantage of the $200 rebate on the 12-35/2.8 at Amazon