I have been blessed to visit the Waiwera springs regularly for three years now and it is just such a treat. Yes, it is basic and it is most definitely not going to appeal to those of you who want a synthetic spa experience. The pools vary from day to day in temperature, depending on the weather. They also vary in mineral composition, and it is reputed that they have differing healing powers. They are not clear water, the sides and floor of the pools are board, and you need to take serious care getting in and out.
The changing rooms are functional and there is no shower - but frankly you should be keeping that good stuff on you for as long as you can and not showering it off :) Do heed advice about taking your stuff with you, and take some water to drink as none is available.
I am glad to hear that the Iwi intends to keep this place as it is, and affordable for the locals. Such a lot would be lost in tarting it up for the tourists, I for one think that it is one of the most special places I know. If you want a fancier place, with less authentic character, then simply go elsewhere. I say this nicely, of course we all like different things:)