I read this German howto on the Canon Digital IXUS und Linux and later on found Gphoto, Canon PowerShot cameras & USB
Then had to recompile gphoto2 since the debian package was broken - contained no descriptions of any cameras!
Eventually, this worked
gphoto2 --port usb: --camera "Canon DIGITAL IXUS v" --get-all-images
The problem was permissions on the USB device that non-root users couldn't read.
Found usb_perms daemon and installed it (linked from the powershot page above)