"When you're a hammer you treat everything as a nail." That's the way I look at every new H.264 camera. The only difference I've seen in Vasiley's GH hacks and this HDMI capture stuff is the reduction of motion artifacts generated by the video compression. I've done tests myself, could never see a difference. So I step back and ask myself, 'what artifacts ever bothered me in my videos?'
The only time macro-blocking annoys me is when I'm watching a video on Amazon, which I paid for, and it slows down to a lesser compression and I see it :)
Everyone has their aesthetic. I have not noticed any H.264 that I thought much better than another camera's H.264 in a similar price range. Of course, there are DOF differences. The Panny cameras are a pleasure to use (but that is ergonomics, not what I see on the screen). I could see the differences in Matt's video above, but I think more a DOF difference between cameras. I do see better color saturation in APS-C cameras vs MFT, but the larger sensors also create worse moire (because of the line skipping). That's mostly a physics problem. Anyway, the difference isn't big enough that it would stop me from filming my Citizen Cane :)
Even H.264 with all I-frames and a 4:4:2 color space is not that much difference from the stock video I get out of my used GF3 body.
Many people, like Skip, get fantastic results from H.264. Getting that quality has to do with photographic skill to me, however.
Just my conclusion so far. There are two major video technologies.
1. ) Compressed video in an 8-bit channel color space
2. ) RAW sensor-data sourced video
There is no in-between. If there was Panasonic would be offering RAW. Why aren't they? The cameras create RAW images in photo mode? Why not just string 24 of them along every second? Why do 4K instead? If you find the honest answer to that question you will see, again, there is no in-between.
I strongly urge everyone to get their hands on a RAW based camera, Blackmagic, or Magic Lantern. Shoot a couple of clips. Ezra Pound said music criticism was pointless because 10,000 pages couldn't describe the first 4 notes of Beethoven's 5th.
Shoot some RAW. Shoot some H.264. Pick which works best for your aesthetic.