I noticed that too; it takes like 10 seconds to generate a "pixelized" (it's still vector graphics, isn't it?) map that I can't imagine taking more than a couple milliseconds to rasterize.
That is really cool and would come in handy for generating data visualizations. But I think it needs to have added attributes for the latitude and longitude of the center of each circle.
Nice. One thing though, choosing a country and setting the color for water also makes neighbouring countries that color, as if a country suddenly becomes an island.
