I wrote a post on my blog about this as well as I can't justify paying all sorts of money for the maps as well. I'm not looking for detailed POI, just a fairly accurate listing of roads.
http://www.tiredofit.ca/2010/02/free...in-gps-device/
In short, It uses the OSM as mentioned above, and they work just as good as the Garmin Maps, and Open Source as well - a cool concept. Installing is simple and they will even work in Mapsource and Basecamp as well!
So far I haven't been sent down too weird of a path in 75 days of touring/relying on its data.