Can't seem to find anything on "IS Disable mode?" in the manual, though. 0-6 options, what are those?
IS means image stabilization. You can typically turn this on and off in the Canon menus on cameras that have image stabilization capability. The script setting was included so that it could be set to your desired value each time the script runs. The script restores the previous setting on exit.
Unfortunately, the meaning of the value used seems to vary with different cameras. Typically it's
0 = continuous, 1=shoot only, 2=panning, 3=off or
0=continuous, 2=shoot only, 4=off
but that's not guaranteed. So do you use 3 or 4 to disable IS? Using an invalid value has been reported to crash the camera, requiring a power cycle restart. You'll have to test yours and see which works.
There has been quite a bit of debate about whether changing the IS settings is useful. There may be some battery savings with it off. The Canon manual for some cameras suggests turning it off when using a tripod as it's not needed and there is a theory that it performs badly if it's trying to stabilize an image that is already stable. There is also a theory that many Canon P&S cameras have "floating" lens elements so IS cannot really be turned off anyway. YMMV.
