Allow user to set order/hierarchy of overlays
If you have more than one layer that occupy the same space, there is no way for the user to set which one appears on top of the other. TNP makes this choice for you, which can create a layer to be hidden under another when you want it visible. For example I have a shapefile for every trail in my state, and others for specific trails (ski, snowmobile, etc.) which I want to be able to choose to be layered on top of (thereby visible) the generic trail layer.