I'm thinking about using these in our backyard.
I'm definitely going to try this. It's perfect for the northwest, where you need drainage in the winter, but also don't want to sink when you walk outside. It's similar to the permeable pavers that a few streets in my neighborhood have been experimentally done with: http://www.portlandonline.com/BES/index.cfm?a=77074&c=45435#photosThey now have a pretty good crop of grass growing through them.
sweet!Look at the border this guy has created. http://flickr.com/photos/87956690@N00/150185442/