Magic Bus

Magic is one of the three major backpacker bus companies in New Zealand. It´s a good "middle of the road" solution since it´s not as hardcore party as Kiwi Experience, and not as expensive as Stray Travel.
Magic has, like all the companies, some pre-set routes, but they will take you along all the major cities and important towns on both the islands. Ofcourse you can always book some extra trips when you´re in a town.
They give you some good discounts on accomodation and activities. Again, all the companies do this, but they change in the amount of discount and in the offering of accomodation and activities. So this could be the thing where you decide your bus on.
You might notice that there is always some rivalry between the busses, especially between the Kiwi bus and the Magic bus. But this is just good fun cause they always try to outrun the other.