Just an update, when you draw that square. You can pinch and expand to a 60MB size I think, Wellington covers up to Levin or something ... I guess it is somewhat helpful.
I still prefer my Nokia than bro's HTC just b/c it has the whole NZ map or multiple countries if your memory card allows with all the POIs and routing ability. May look at a bluetooth gps receiver to get a quicker fix.
I also find that a Navman or TomTom is better for NZ travelling cos it just works, works without 3G, has the whole NZ/AU map, works in area without cell towers like parts of the remote areas.