Hey, a Debian user reported (http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=625794) that he had wrong spacing between launchers on a vertical panel with arrows on the side. Apparently it seems that the arrow space is added instead of substracted (he attached a patch which isn't a unified one, though it shouldn't be too hard to fix that).
Created attachment 3655 fix spacing in vertical panel with arrow on the side Here's the unified diff.
Not really like I had it in mind while writing the code, but it does indeed looks better. Applied in be44541.