Not sure if any of these questions got answered elsewhere on the forum, but I'd like to chime in with some of the answers that I've discovered myself:

1) Those of you complaining about the lack of constant preview on this camera (especially when working with manual glass), there is actually a "preview" function which can be mapped to a fn button. Antonglamb mentioned it above, but the responses that came afterwards appear to have missed that nugget of wisdom. I mapped my AE/AF lock button to that (because it is conveniently placed, another good option is to map the Wifi button), and now when I'm shooting stills I just hit that button for a live preview of the actual exposure I'm going to get. Its funny how it works, the live view sort of slows down to like 5fps when preview is on- I'm guessing that's a feature to illustrate how your motion blur will look since there is a noticeable gap between displayed live frames for you to judge any kind of blurring. Almost like it is constantly taking a picture. I'd actually rather it didn't do that because I just want to check my exposure and the slow refresh rate is annoying, but totally works perfectly if you want to adjust your exposure and see the results in real time.

2) The 720x480 videos coming off the G6 are some sort of Windows 7 bug. It reports that 1080 24p files are only 720x480, and therefore WMP only plays them at that size. But you'll notice a lot of aliasing because the screen is being forced to play at the wrong size... if you full-screen the video, you can see the resolution is all there. Any other app you throw it into (Sony Vegas, Premiere, VLC, etc) all recognize the 1080p resolution, so this isn't a G6 fault, its something wonky in Windows 7. Windows 8, for the record, reports the proper resolution. And a 1080 60p file is correctly reported, so it is just a bug between 1080/24 and Windows 7 that has absolutely no real derogatory effect on anything, other than scaring the pants of a new user who thinks they ruined their shot in low res!

3) Battery thing that Chungda mentioned is not a real thing. I'm guessing the contacts on one of the batteries got dirty (I've had that happen on my Canon bodies as well). So putting the old one back in seemed to work, but the new one did not, because the new one probably wasn't making contact. I have 4-5 batteries between this and my GH2s, and I swaps them freely all the time, some after market, some genuine. It doesn't care. In fact, the G6 has an advantage over the GH2 in that it reports battery life on aftermarket batteries. The GH2 wouldn't tell me how much juice is left unless it was an official battery, which was a major risk on a paying gig. The G6 happily tells me, and warns me when it is getting low, and shuts down when depleted just like an OEM battery. Nice!

4) Starsailor, that sounds like frequency collision between the lights and your shutter speed. That can happen on any camera. The lights are flickering at a refresh rate your eyes can't notice, but the camera's shutter is capturing it in the middle of a refresh phase. This is the same reason we used to see the scan lines moving up or down on a TV or old computer monitor in a video recording- the refresh rate between the display and recording are colliding. To fix this you need to either change your shutter speed or the light source. It has nothing to do with ISO.

Again, I apologize if these are well known and already answered elsewhere in the forum. I just noticed that no one was coming back to answer these questions here so I figured we should tie up the loose ends for future readers!

@dishe thanks for putting the answers in 1 place!

Sorry that I might late to be here, but I just got a G6 Japanese version and there does not have English language to switch. I also spent some hours to search around G! this problem, but did not get any lucks. At the end of searching, I found this place and would like to know do I have chance to hack Japanese to English language for my G6 at this time?

Thanks @yskunto replied me quickly. That's poor me as others who had Japanese version cameras at this time, but still hope @Vitaliy will release hack for that model soon. About return item is not big problem and I can get Asian PAL version, but it is still quite expensive right now that's why I got Japanese with cheaper price. I don't use video function so I don't mind about it.