You should by all means try to visit the Catlins if you are on the S Island, and if you visit the Catlins you should definitely stay here! We didn't have reservations and picked this rather randomly … and when we got there, immediately wished we could stay for longer than a night. We did happen to meet the owners on check-in and out, and thought they were lovely. The other reviewers have mentioned the main selling points - penguins, dolphins, beach, solitude - all of which are fantastic. Many have also mentioned the weather, which can be very iffy (we got lucky).
The one main point to reinforce is that you should stock up on supplies in Dunedin if you can. The closest supermarket (I can't remember the town) is quite far away from Curio Bay and pretty lacking. The nearest restaurant, about 8k away, was unexpectedly closed the night we were there. There are no shops or other eating options anywhere in the area. Luckily, there was a little takeaway shack that happened to be open during the summer, and although the food was terrible at least it was something. So, stock up, plan to stay a few days and enjoy relaxing in a remarkable spot!More