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 so there was an adjustment period when getting up-to speed withe cseam3d's API/APIs compared wih others available out therde too :).
But once you get your head around what APIs mean where they come into play etc then everything becomes much clearer than any manual process would everbe able touse them properly againtothers :).