I am surprised at the rating you gave the garmin nuvi series, I have been looking at buying a gps device (nuvi660) and found that the nuvi series (300 & 600 ) can't save a trip plan and you can only have 1 waypoint in a trip plan. This of course means that there no trip or itinerary planning functions at all. The other units I looked at, the navman and tom tom (both cheaper than the nuvi ) have both these features, saving a trip plan and multistop trip.
When I contacted garmin by email enquiring about the lack of these features the response was by not including these features the nuvi was easier to operate.