My girlfriend and I (20 something year-old students) arrive Auckland Dec. 31 and have until Jan 14 to experience as much high adventure, beauty, local culture, etc etc as possible. We are prepared to spend all of a couple hours on the north island if we should immediately head south, but do want to experience some of the north island, i think.
Specifically:
1. What might be considered the top 3 places to spend New Year's Eve in NZ?
2. What are 3-5 must see vistas?
3. What are 3-5 must do high adventure activities and where should they be done? (We will try anything!)
I might mention that we have a flexible budget; value is most important. We usually stay in the cheapest possible guest-house or hostel, eat decently, and spend a lot on moving around and doing stuff. We probably average 2-3 nights per town, so a 5-7 city itinerary is realistic. We dive, bike, hike, paddle, etc. We don't prefer tourist tracks, but realize it is busy season and our time is limited.
Any and all suggestions appreciated!

OP, I think a better way to go about this would be to look through a guidebook, narrow down your options according to what appeals to you, and come back to the thread with more specific questions. However, a few tips to start. First, with only two weeks to work with (a large part of which will be spent in transit) you'll want to steer clear of the major cities except as bases for the excursions that interest you most. It's not that there aren't plenty of things to do in Auckland, Wellington, Christchurch, etc., but they're just cities, no more interesting than cities much closer to home. Definitely give Rotorua a pass.
Also remember that even though NZ is a small country, it's an extremely mountainous one without freeways, so it does take considerable time to get from place to place. For two weeks, I'd narrow the trip down to two or three smaller regions. Don't write off the North Island altogether; it has the best swimming, snorkeling, and diving (Goat Island is no Great Barrier Reef, but it's a good excuse to head north of Auckland) and perhaps the greatest one-day hike on earth (the Tongariro Crossing, on the central plateau). Also, if you want to see a lot of contrast in one day, Taranaki has a bizarre combination of surf, rainforest, and snow-capped peak in a small area.
For the most iconic South Island scenery, Fiordland is a good base for both multiday treks (you may have time for one) and all manner of adventure sports and tours. Queenstown draws the biggest "high adventure" crowd, so if you want to do a lot of that stuff without moving around too much, it's an option. The Nelson/Golden Bay area is perhaps the most mellow, delightful, and beautiful part of the country - not so much the huge peaks and glaciers and such, but it's a good combination of small-town local culture and diverse outdoor activities.
If you're arriving in Auckland on New Year's Eve, then you might as well spend it there. It's a mellow holiday for most, good for a barbecue on the beach if it's dry, and there will be enough going on around town if you're not too jet lagged.

There are certainly things worth looking at in the North Island, if nothing else it is worth taking 2 or 3 days to travel through it so you get an idea of what to see next time you visit, some good geothermal stuff around Tapau and lots of culture in Wellington. Accommodation is generally good, cheap (compared to UK) and varied. The place we stayed at Franz Joseph village had everything camping, bunk rooms, chalets all on one site, I think we paid about £30 per night for a 4 bed chalet, camping was only a few pounds. I think that is fairly typical. You can get an AA accommodation guide out there which is pretty comprehensive. Loads of activities to do, but if you want to do some of the big hikes book them up in advance, most only allow a limited number of people on route at any given time. Get yourself some good guide books and enjoy - so much to do and an excellent place. Queenstown is a good spot to wind down (!?) have a beer or a coffee and plan all the other activities - it's a hive of activity and life.