Ok mate. Thanks for letting me know.
I dont see how running this script prior to installing an ICS rom would cause any issues however, especially if you were trying to go from GB to ICS. If you were already on ICS and run the script then flashed another ICS ROM, then I can see this may possibly cause problems if ICS has totally different areas that need clearing.
I can't test anything until I go over to ICS myself. I won't be doing so until CheckROM release their ICS version.