Here is a video taken using the 50 Mbps 108060p MOV mode of the GH3. This mode uses the same sophisticated compression as AVCHD (CABAC, high profile, 2 reference frames, etc.) but packaged as MOV and at a bitrate that is almost twice as high as AVCHD 2.0.
Can you see any difference in quality compared to 28 Mbps AVCHD? You can download the original file (re-wrapped as MP4, but not transcoded or re-compressed):
I remember having horrible pixelation with the SD600 on red-colored objects when there were lots of other moving details in the image. Since then Panasonic seems to have fixed their codec, but you may try shooting red objects. Interesting, I have the Nikon D3200 breaking apart on red objects as well sometimes. Both use AVC. The Nikon was 24p @ 22 Mbit/s.
No 4:2:2 color in any mode, including the uncompressed video through the HDMI port.
This sucks. 50 Mbit/s should be enough for 4:2:2. Canon and Sony offer 4:2:2 @ 50 Mbit/s with MPEG-2, not even AVC. This, and no peaking on the GH3, makes it easier to prefer the G6 over the GH3 ;-) Although I cannot underestimate the importance of high bitrate.