Some people have complained about the randomly disappearing CHDK overlay in some situations, mainly when looking at the CHDK menu. This appears to be caused by the Canon software updating the screen while CHDK is active. The easiest way to see this is to enable face detection and go the CHDK menu (do a Google image search for "face" and point the camera at the monitor). You will see transparent holes punched in the menu when the brackets around a face are drawn. This does not happen to the OSD information because the OSD information is continuously redrawn.
As an experiment, I did the same continuous redrawing for the menu, removing the line "gui_menu_redraw=0;" from gui-menu.c. What I found is that the menus immediately heal themselves when pieces of the menu are erased. In addition, there is no noticeable flickering or sluggishness caused by this change. A similar thing could be done in the text reader, games, palette, etc.
Is this a reasonable thing to do for all builds?