CHDK doesn't change the firmware, and there doesn't have to be something wrong to use it. It adds functionality
1. The link you sent also has a link to firmware updates
2. And to quote the website: "CHDK is a
firmware enhancement that operates on a number of Canon Cameras. CHDK gets loaded into your camera's memory upon bootup (either manually or automatically). It provides additional functionality beyond that currently provided by the native camera firmware."
And the warning: "Some users have reported permanent camera damage which may be connected to CHDK, see Camera failures suspected to be caused by CHDK This is not certain, proceed at your own risk."
So i repeat: Its not worth bricking your camera.