[*]Update – have used Garmin 500 a few times now. Seems to work well. For road cycles I load my GPX (created coarsely in memorymap) into MapMyRide. It can then snap the route to the roads. Then I export as GPX (just save over the original file) and load into Garmin for verifying and sending to the GPS.
Post ride I only import to MapMyRide. Seems to work well.