The Garmin Nuvi 300 is neat, tidy and simple to use. It'll generally get you there just as long as you use a little bit of common sense.
I would recommend turning the back light timing down to minimum (15secs) if using without the in car power supply as the battery doesn't last that long. The back light still comes on automatically at junctions etc. Even on minimum.
I would have given it an 8, possibly 9, if it weren't for the extortionate cost of the map updates.