Both Islands have a lot to see, but if you are going in winter and have less than 2 weeks, concentrate on the South Island.

If you go to Queenstown, which I suggest you do, spare an afternoon and drive to Glenorchy. There isn't much there, but the road and landscape are fantastic!

Also, from Queenstown, take a scenic flight to Milford Sound (which involves a flight to the sound, a boat cruise along the sound, and flight back again) Awesome views from the light aircraft.

If you have more time it is worth driving from Queenstown to Te Anau, staying in Te Anau overnight, Driving to Milford sound (again, wonderful roads) doing the cruise, then being back in time to do another boat cruise on Lake Te Anau to see the glow worm caves.

Lake Tekapo and Dunedin also worth a look.

If you stay more than overnight in Christchurch, do a drive to the Akaroa Peninsula. (in winter) You drive up a mountain, into the snow, and then down into the town of Akaroa. Shit coffee, nice ambience. Then if you have time, drive on the roads that lead up to near the Christchurch cablecar summit. Nice and windy and sure to piss your passenger off

I've got a few pics of Queenstown / Tekapo / Christchurch area here, although the last two (of Skytower) are Auckland

http://www.flickr.com/photos/2642477...7604976500436/