I'm looking to go to New Zealand in May. Besides the obvious December-February months, is going in May good? Will it offer me all the same accommodations and activities as the summer? Is it deserted? I'm 22 and going by myself. I plan to take the buses around, will they be busy or awkwardly deserted? Any thoughts on this time of year or why I should wait for the summer?

NZ is good anytime of year. I wouldn't hesitate to go in May. In fact I have.

Gone in April it is nice fall weather. Suggest staying at YHA and BBH hostels (check the ratings websites for reviews) to meet people.

Sorry to be so short Mchurd, I was trying to get out the door when I responded.

Regarding your other questions:

Generally you'll have no trouble with accommodation or activities, however, there will be a few exceptions.

Although the walking tracks don't close per se, some become inaccessible for the average tourist. For example, the boat that takes you across the lake to the beginning of the Milford Track won't be operating, so the only way to get there is to arrange private transport ($$$) or scale a few mountains.

Milford Cruises run year round, and May shouldn't present any major weather problems unless there's a freak snowstorm or something.

Water taxis also operate year round (Abel Tasman, Queen Charlotte Track), but just on a reduced schedule.

A handful of restaurants close, but usually not until June, July, August.

The advantages are fewer people, lower accommodation rates and potentially good weather.

Mel, as usual, has said pretty much all that is needed, except that it will be getting cooler then and you may get some early snow in the high areas. We have been to the both island in winter and had no problems, but we did have a campervan. The North will still be quite nice.