The CHDK add-on implements new features like RAW, battery indicator, live histogram (RGB/luminance), zebra mode (blinking areas of over-/underexposure), DOF calculator, scripts (intervalometer, exposure/focus/... bracketing etc.), Tv, Av & ISO overrides, text reader, file browser, calendar, games and much more. There are now several different builds, implementing features assisting taking 3D-Stereo photos, motion detection etc.
The CHDK firmware add-on does not touch the original firmware of your camera. It is an additional program which gets loaded into the memory of the camera.
These details are provided for information only. No information here is legal advice and should not be used as such.