I've installed a lower 44mb hack which is tested and completely stable. Initially I tried installing the 176mb hack but I didn't do it right, I don't think, I'll try it again later. The higher bitrate hacks are still going through testing, so their settings haven't been perfected -- which can result in frames being dropped or going white sometimes. The 176mb hack only came about around a month ago, and it seems like every week progress is being made in improving it. SanDisk Extreme Pro cards are recommended to use with the hack, especially at the higher bitrates. It seems totally trial and error, though, as I've heard of people just doing take after take to get something usable (without errors in the recorded video) especially at 176mb. I'm not really sure about the frequency of the errors, but people have advised against using the 176mb hack for time-sensitive professional purposes.
As long as your camera doesn't lose power while updating the firmware (it's recommended you use a fully charged battery and not AC Power while doing it), there's no danger in damaging the camera. If power were to disconnect while the firmware was being updated the camera would need to be sent back to Panasonic to be serviced and reset. Reverting back to the original firmware or to a lower level, more stable hacked firmware is as easy as copying a new file to your memory card and loading it up.
I've seen some still comparisons -- if you can get usable footage I think it's definitely worth it: even at 44mb the detail in the images seems to dramatically increase. The biggest difference I see is in the blacks and shadows...whereas at lower level bitrates (and especially at the 24mb the camera records out of the box) low light areas can become muddy, the higher level bitrates allow for smoother, cleaner blacks.
