I have a nurse working for me who didnt seem to have any problems. You just contact the nursing council which is in wellington and my belief is that if you have a visa then the registration is nothing but a bit of time. Obviously there is paperwork but my friend didnt have any trouble. The salaries are about to become equal all around the country and therefore it seems sensible not to work in the most expensive areas to live ie the big cities. We have moved from auckland to new plymouth and the costs are a lot less and I dont have to pay to park at work! There are jobs everywhere, more prevelent in the big cities but sometimes the working conditions are harder there too.
Hope this helps, let me know if there is anything else you need.