Hmmm this should be noted as NZs ONLY drawback surely. The Katipo Spider can be found throughout NZ and if bitten by one, it can cause redness and slight swelling around the bite, similar to a wasp or bee sting. They tend to make there home in sand dunes around the coast, so it is advisable to wear flip-flops or sandals if walking on such terrain.
Perhaps more worrying is the arrival of the Australian Red-Back, on cargo ships from Australia. If bitten by one of these it requires immediate attention or anti venom as this can cause severe nausea and soreness. However the various New Zealand Environmental agencies are very aware oif this and track any poulations closely. It is known that there is a small population concentration in the central Otago region (South Island) and an even smaller one around New Plymouth (North Island).
Hope this doesn't alarm you too much, they are very prominent in Australia and people get on with them there. ::):