We used the Bluebridge ferry service from Wellington to Picton and then return. The service is normal not that great i would say. Interislander i believe is a bigger name and have the monopoly for the route, Bluebridge had to travel a bigger route. I would advice to bring your own food and drink for the travel as it is bit expensive. It can be bit crowded once filled up and it was a struggle to get a seat. Overall experience was not that bad.