Needless to say this is a feature we’ve been expecting for a while. A transparent, filled, polygon is something that many people have been trying to do for a while now, none of which were more than polyline or overlay hacks. The nearest we came was the state overlay demo that Mike explained in September.
I’m hoping that Mike can revisit the shape files example and do a GPolygon demo as a compliment to the custom tiles one from September. The logic of the shape-file parsing is still valid, but the rendering mechanism would be completely new.