As a local rider, the correction is that you want to ride HWY22 (not 23) you want, and its just under 100kms of NO STRAIGHTS. Windy and fun, road surface is generally quite good, and very little traffic. Finish off in Whaingaroa/Raglan. A great escape from Tamaki/Auckland and can be done in an afternoon.
Stunning views on good day (about 50km to each side on the ridgelines) stacks of twisties through to SH23. The local roading guys fix bad seal by covering it in gravel and letting the cars/trucks pack it in. A few days ago (4/1/2012) they had put out a sign warning of this - that's the first one ZI've seen in three years of riding this road. Traffic extremely light, but farmers use both sides of the road when cornering. Not a good road for a rookie rider. Enjoy