Hi Cloud 9,
We are regular travelers to NZ. The north island is not to be ignored and the areas around Lake Taupo, Mt Rhuapeau, and Hawkes Bay are all fantastic. If you are a fly fisherman, you can fish in the waters around Lake Taupo all year round. In July last year, my son and I had a fantastic few days fishing there in between some skiing. NZ also has some premium golf courses if you are into that ^&%$$@ sport. The Bay of Islands north of Auckland is magnificent but perhaps better in Summer.
The south island has loads of premium destinations. Queenstown has plenty to do and see as Eric mentioned, not to mention being home to some very fine Pinot's if you are into that. My family like to trek and NZ has to be one of the best places in the world for this however, your time is really getting too late in the season for the more spectacular treks. There are loads of amazing day walks in the Queenstown area as well as the area around Mt Cook which is a great place to stay a day or two mid trip. The West Coast has some pretty wild and spectacular locations that can be tough if the weather turns bad. If you had that way, you can cross the West to East coats via one of the passes (weather permitting).
We love the north end of the South Island as well. The beach town of Kaikoura is beautiful (but more a summer location) and the drive north from Kaikoura through to Marlborough (home of the fantastic Sauvignon Blac), Picton and The Queen Charlotte Sound area is stunning. Picton is where the inter island ferry from Wellington arrives. We have done the drive from the north, across on the ferry and then south a number of times. Wellington (bottom of North Island) is a neat city as well.
I can say that you will totally miss your 968 (I always do). The roads are very good, amazing scenery and hardly any traffic. Having said that, we always end up with a Camry due to its reasonable hire rates and massive trunk (we are a family of 5).
An finally, my last piece of advice is to have a very flexible itinerary and simply go where the weather is. NZ is amazing if you get the weather and this can vary a huge amount with only a few hours drive. We once were chased out of the mountains by impending flooding and ended up sunning it on the beach at Akaroa (on the Banks peninsula near Christchurch) after only a 2-3 hours drive. The West and East Coasts can get different weather patterns and our experience is that the weather operates on a fairly short cycle (about 3-4 days). We tend to have plenty of flexibility when we do our back country treks and leave the day the weather starts to clear ensuring we get a good run.
Don't sweat accommodation, we never book and simply turn up at the government sponsored i-Sites that are in pretty much every town. They are staffed by locals, are very helpful and will determine the type of accommodation you need, organise it there and then, and away you go. We have never missed and usually score far superior accommodation than we would have booking remotely online. This is absolutely the way to see NZ.and makes the best of what is a super friendly country.
After writing this, I am going to speak to my wife right now about which trek we need to do next!! Big fan as you might have gathered.
Have fun. Let me know if you want any further info.
Ciao!
Peter