Currently, applets and launchers are positioned by a pixel distance from the left (top) or right (bottom) edge of the panel. While this works for preconfigured panels, where these distances are set in gconf to 0px, 1px etc it's difficult to make changes by DnD or adding applets without losing the consistent look.

imho practically always the user wants objects on the panel to appear in stacks growing from the outer edges (except, maybe also centered). Removing or adding objects to one of the stacks should always keep them grouped with no spaces between (which can be achieved with spacers).

I propose to keep the current gconf format for compatibility, but check
   * when an applet is added, if it is close to one of the stacks and if yes use the incremented position of the last element in that stack
   * when an element is removed, check if it has an applet directly "panel-inwards" from itself and if yes move this and all following applets outwards.