You lucky man! I long to go back.

The lower portion of the south island is stunning. Lake Wakatipu is absolutely without peer for photos. If you get up to the head of the lake there is the Gelnorchy Paradise area on the eastern shore and Kinloch/Caples/Routeburn on the western. Invercargill and Bluff are wonderful too. StanW lives in Invercargill and kindly put me up and showed me around when I was over there in May 2010.

I have a big set of photos from my two trips over on my RedBubble Gallery.

About the only area I have not been to is the north east of the south island, so cannot advise you there. Kaikoura on the east coast is wonderful too.

I found the light to be amazing on both trips (Aug/Sept 2009 & May 2010). I'd advise taking all your lenses if you can, you won't regret it. And the dawn light is fantastic there.