hi, just gave this plugin a test run.
I chose to use the url of a kml file. The map and map icons show when you preview the post - but when you publish the post what you get is a grey background with just the icons showing.
I also tried publishing a post with a custom map and input the full address as instructed, then published. This time, the map and icon show but you still have a large fuzzy area of grey that surrounds the icon, with the rest of the map outside.
This is the link to the first map http://www.hub-works.net/maptest/test-map-2-sign/