A few things...
CHDK has to be on the sd card, so, if I replace the card without access to a computer to put it on the card, I have the bad pixel.
Also, to have CHDK load on startup, the memory lock of the sd card has to be on, and it has to be switched back off whenever the card is being accessed by the computer to allow the computer to delete files on the card. I worry about that switch wearing off in the long run. And it's a hassle.
Does that make any sense?