Nice summary Trunk, will be helpful for sure. I picked up a GX1 a few months ago to experiment with and have been pretty pleased with it and the Panasonic 14mm pancake lens. Very lightweight compared to the Canon 30D/10-22mm I was using on occasion. Not quite the same quality, but good enough. I really like the 4:3 aspect ratio, but that's personal preference. A few observations in the dozen or so dives I've done with it...
1. The remote shutter needs an adapter to work with standard switches, but not very difficult to make. I built one from a connector I bought at Radio Shack, a couple of resistors, and a 2.5mm right angle plug I ordered online.
2. The Custom modes on the dial is nice, it can be programmed with most camera settings you need for skydiving, such as manual mode settings, disable touch screen, JPG format, etc. Except for the manual focus point, that needs to be set every time you let the camera auto-focus. Pretty easy though, especially with the zoom feature, and it will remain in place after power off. All the lenses (that I have) are electronically focused, so moving the zoom ring with the power off doesn't affect it. There's no reason the manual focus point could not be part of the custom settings, but not something they figured people would use I guess.
3. FPS is a bit low, but perfectly fine for me. With my SD card (class 10 Sandisk Extreme) I get about 5 seconds at full rate, then about 2 fps after. I clears the buffer pretty fast though, so it's nearly always ready for full-burst shooting. I should note it does have a 20fps shutterless burst mode, but quality is poor. I would be tempted to try the Olympus PEN models if you need a faster fps.
4. It has an auto-ISO feature in all modes EXCEPT in manual mode. Which sucks, because it'd be nice to lock the shutter and aperture and have it auto-ISO the exposure. As it is now, I guess at a decent ISO depending on light conditions so that my aperture remains high enough for a decent DOF. I hear the Olympus PEN models have this feature though. Since it's just a firmware issue, I contacted Panasonic and actually got a reply saying they forwarded it to their R&D department, who knows...
5. Good ISO performance, at least as good as my 30D I'd wager, even though it's a smaller sensor (2x crop factor instead of 1.6x). I have no issues using 1600 or 3200 if need be.
6. Did I mention it's small and light? I don't even notice it on my head until I smack it on the ceiling or door of the plane. D'oh!
7. The SD card slot is on the bottom of the camera, so removing the card is a pain. Not really an issue for me, but a working stiff might be a bit frustrated.
Overall I'm pretty pleased with the results. It's not quite in the same league as my 30D, but the more I've used it the more content I am with the new format. The smaller size is priceless, though it's not really much cheaper than a standard Canon Rebel setup.
I was a bit bummed at there being no inexpensive options for super-wide angle, but you can pick up the excellent Panasonic 14mm from Ebay for a good price and slap a Panasonic DMW-GWC1 wide-angle converter on it to get to 12mm (24mm equivalent) without adding much extra weight. The attached pic was with the wide-angle attached. ISO160, 1/640s @ f5.6.
-dg