Works good and API is very simple and straightforward.
I have having the same problem as the user PlaceblockHD said below. I add the glow to a player and only add one viewer, but some reason everyone on the server sees a white glow around the holder and it does go away.
Also, when a player goes into 3rd person they can see a white glow on themselves even if they are not a viewer and the color is also something completely different like red. And its not going away after I remove them as a holder.