Very easy to create complex geometries, great documentation (though it could be more concise), good examples of use cases with real world data sets like Google Earth or OpenStreetMap; very flexible tool that can handle even some pretty advanced functionality such as vector rendering from raster images - though beware because this has not been tested thoroughly yet! It does have its quirks but these are mostly due do how Javascript works which we love anyway ;-) I've used other tools before soβ¦