My wife and I stayed overnight on our way from Christchurch to Franz Josef.
Everything about our stay was great, you can tell from the moment you arrive that Sarah and David have put a lot of thought and effort into the place to make your stay perfect. Breakfast (in the form of eggs, bread, fruit, milk and cereal) was waiting for us on our arrival after their adorable flock of sheep greeted us at the parking pad.
It was a chilly night but the heated mattress pad worked wonders and if it hadn't, there were extra blankets galore in the train car. They also had sandals ready for hopping over from the train car to the bathroom, and umbrellas ready in case it rained. There was bug spray available and they even had some outdoor blankets in case you wanted to sit out by the pond and warm up.
Every detail seems to have been anticipated to make your stay a delight. We were sad to leave after just one night!