Just received the maps for my 605. While waiting for the maps to show up I managed to find "Garmin Bobcat", a beta routing and waypoint program for the Mac. I just finished creating a route expecting to then have to convert it to a course since it is about 100 miles, but it seems to load without any issues. Routes that I have tried to load from MapMyRide.com would generate errors and none of the turn markers would be correct.

I am thinking that routing may work for longer rides providing the route only consists of waypoints and does not have track information in it. I'll be testing this out tomorrow and will post how well this works out.