Have only been to Queenstown (about 8 weeks ago) which is a pity, would love to campervan around NZ for a month. The whole area is very CV friendly btw.
Worth every cent and even though QT is rated as exxy by NZ standards - when you are from perth it is bloody good value.
Activities, food, sights, hospitality, prices are top notch. If the rest of NZ is half as good as QT it is worth going.
Ditto on Otaga pinot noir, if you are a fan of resiling you are in for a treat in NZ also.
Would be back there tomorrow if the $$$ were available.
Do it cuzzy bro.
Like others here have suggested - go South, get into the mountains. Do some overnight hiking - Routeburn good if Milford sound is booked out, there's a nice one up Mt Olivier near Mt Cook, and Queen Charlotte sound.
If you like wildlife go to Kaikoura and see some whales and dolphins.
There are loads of awesome things. And it's not particularly 'touristy' despite being such a perfect holiday destination. Certainly not compared to Europe, Asia or North America.