Easy to use, extremely configurable and makes any google map look great on your website. You can check out my website to see how I am using it.
If there was two features I would love added to it, they would be:
1. The ability to add your own customized routes to the maps.
2. If Google hasn't got a correct location for an address (this is normal in Ireland because the guys who built this country decided that addresses aren't really important), and so you need to use long/lat coordinates, that you could create a custom address so that when someone mouses over the map, they don't see the long/lat coordinates but the actual address of the location.