Very cool! I've been looking for a way to replace the anchor icon to the left for ages now - imo it's one of the few things keeping Docky from being perfect for customisation. Does your "hack" still work for the latest versions of Docky?
I only tried this trick a couple of times, but you have to manually change the anchor icon, and with Docky's fast updates rate, I couldn't do everytime, plus it's not perfect (works only with 110% or below zoom levels).
Um, I don't use docky anymore(I'm now a prode DockbarX user ) but I think it will work with no problems IMHO.