Looks like this setting is going to be specific to each skin, language and Start Panel design,
if you want to skin the All Programs menu item button.
That one can get it to work at all is a local miracle it appears.
The offset produces one effect which is annoying when using a right-edge vertical Taskbar, which happens to be my preference, of course.
Before I decided to clean up my All Programs menu (what a hash Windows default behavior makes of this - another story), the primary menu would fly open half way across the screen to the left of the Taskbar. I assumed this was because of the negative offset for the All Programs menu item button fooling the OS into thinking the left edge of the All Programs menu item button was out there & the menu was opening to the left of it (as you'd normally expect). Having let Windows Installer have its way with it, I also had such a huge primary menu that it took up 3 columns.
Once I cleaned up & categorized my All Programs menu & submenus, using short category names only for the primary menu folders and showing only those folders on the primary menu, the primary menu now opens off the right side of the All Programs menu item button where you'd expect it to, since it is narrower than the width of the Places pane of the Start Menu. If the folder names are long enough for the menu to end up wider than the Places pane, it will open off to the left, offset by the number of pixels designated in the All Programs menu item button attributes.
It appears this only affects right-edge vertical Taskbars (which makes sense), so if there are any other oddballs like me out there using a right-edge Taskbar, this information may prove useful.
