When we told our motorhome company that we would be staying in Hamilton for a night, the lady pulled a face and said 'We call it the Tron, there's not a lot there'... she wasn't wrong, but even in hindsight we wouldn't have changed our plans. We needed to get close enough to Auckland to ensure we didn't have a long drive the next morning and Hamilton was geographically the best location.
We arrived late, having stocked up the campervan with supplies for the evening at a local supermarket. The campsite seemed to be full of people doing the same as us and using it as a quick overnight stop, and some people who seemed to be staying much longer term.
The campsite is what seemed to be a residential area, just off a busy road. It's leafy with clean amenities and a large communal kitchen. My only complaint is that the showers are like those you get in a swimming pool - decent enough pressure but you have to keep pressing the 'on' button, otherwise you only get about 30 seconds of water. We had read beforehand that other campers had been unhappy with this, so we knew what to expect... but they should be ripped out and replaced with proper showers. I'd rather have paid a few dollars for 5 solid minutes of warm water than put up with continuously pressing the button... the squeals and cries of frustration from the other ladies in the cubicles would support this theory.
By all means stay if you're passing through but if you're looking for somewhere to kick back for a few days, there are more picturesque locations to park up.