Nelson's lovely, but I can't get over Wanaka as the place to be in NZ. I've only visited there a few times, but I always leave thinking 'this would be a great place to settle down'.
Wanaka is really beautiful; for people who haven't been there you can get a reasonable idea of what it is like by watching almost any of the outdoor scenes from Lord of the Rings / Hobbit movies. I first went to Wanaka in '94 long before the rest of the world discovered it. Warbirds over Wanaka is great too if you're into WWII aircraft (and others besides). The skiing is great there too (Cardrona, Treble Cone). And Hilary's first major ascent was Mount Aspiring which is about 1.5 hours drive by 4x4 from Wanaka.
