Spent half a day here over the Christmas break... I'd recommend half-day trips unless you're planning on doing the Queen Charlotte trek.
While you're on the island, make sure you put aside enough time for coffee and breakfast at the lodge - there were 7 of us at breakfast and none of us left disappointed with our meals. The salmon bagel was a special favourite.
Lochmara Bay Marlborough Sounds Picton
Restaurant Association of NZ
Tourism Industry Association