Hit and miss at it's finest. I've experienced utter chaos unfold at the train station when faults have occurred and no one knows what's going on. The buses are even worse mainly due to their unpredictability and the mood of the drivers. Occasionally I'll have a good experience but for the most part using Metlink leaves me feeling queasy. One up for them is their online journey planner.
This outfit runs the bus services in Wellington. Not sure if they are council owned or private. Either way, every bus that I caught on my stay in Wellington was on time, clean, tidy, modern and the drivers were friendly. Fares were entirely reasonable and the frequency of the service was great too.
1 Hinemoa St Wellington