Performance: Improved the update method. Previously the gps arrow would update 20 times a second whenever you were moving. This has been greatly optimized and it now only updates 6 times a second only if you are moving. The new implementation allows for GPS compatibility with plugins that have vehicles not marked as a vehicle in their code. In other words the GPS supports all movement/vehicle plugins (teleportation plugins not included).
The entity rendering in 1.8.x clients are for some reason different than the rendering in 1.9 and up clients, which make the arrow appear slightly messed up for 1.8 users. I am working on a fix for this.