In planning a recent journey using RoadTrip I was disappointed to discover that the Nüvi 350 does not accept downloaded routes. Determining why my laboriously constructed routes weren't showing up in the 350 took quite a lot of digging in the specifications; an error message when I attempted to download them would have been helpful.
If I had been aware of the 350's lack of the route-storage feature, I might well have selected another device, but the 350 is my first GPS navigation device, and as a novice I missed the significance of that missing feature.
I hope these observations may be useful, and in any case kudos to Garmin for its accommodations for the Macintosh.