He said Auckland's structure had been in place for two years and if he had any concerns it would be the lack of funding and impact community boards have.
"I think long-term the amalgamation for Auckland was the right thing," he said.
"I don't think we've got the model 100 per cent right yet."
A few members of the public questioned the impact on rates with Auckland's changed local governance structure.
Mr Barnett said the council went through a smoothing-over process, which meant there was a very short-term increase on rates.
Another person said the Wairarapa public consultation process had turned into a "community confrontation".
Mr Barnett warned residents to be "really careful of what people can promise you," and to keep discussing options for governance.
Wairarapa Chamber of Commerce chief executive Stephanie Gundersen-Reid said it was an honour to have Mr Barnett speak to the crowd.
"We're not saying anybody's idea is bad, we're just saying taihoa a little bit and let's work this out."
