Brian you are correct. The latest Ptools allows you to set the camera to accept all hacks after the initial one as version 0.0 so genuine firmware will reload. You may still have to renumber the genuine firmware - this is unclear.Thanks for the summary and link Herman.
As far as I know, the firmware can be reverted back to original state - so unless the camera breaks down and needs repair with hacked firmware installed I don't think I would worry about loss of warranty.
As for image quality improvements in video, they seem to be dramatic.
Cheers
Brian