I already told you, that Picton is the gateway to the south island. The ferrys from Wellington head into the sounds and drop of all their passengers there. Only a small percentage stays in town though. I came to quite like the little, quiet city and stayed quite a few days before finally heading off south after returning from working in Blenheim. Picton has some decent walks just around the city, including the Snout Track, leading you up to Queen Charlotte View about 10 km out of the city.
But the views from town are by far not comparable to the ones you will actually get, when you head out in to the sounds. The Queen Charlotte Track is one of NZ's more popular tramping tracks, but no great walk, thus not totally overrun by backpackers coming along. I headed out on the track for 2 days only, due to the lack of proper camping gear. Never the less I got rewarded by two great days of (not to hard) tramping and awesome views of the sounds:
The view from Ship cove, the drop off and starting point of the Queen Charlotte when walked from North to South.
Schoolhouse Bay Campsite view, one of many beach stopovers on the first day.
Camp Bay, after 27.5 km the first considerable campsite on the track, usually stopover for all the trampers with tents.
Decent track, not to hard on you if you're doing lodge layovers, quite long days out on the track if you're camping. Gorgeous views of the sounds and lonely beaches for a quick swim. Definitely recommended ;) Don't forget to have a look at the South Island Album for more pictures of Picton & the Queen Charlotte.