I bagged this one over the Winter (July I think). At least I think I did. The GPS on the phone said I had. The problem is there is nothing to mark the summit and it is such a rounded peak that there is an element of guess work required.
The track was a complete bog in a number of places and lethley slippery in others. The return across the back of the dunes requires fording an overflowing marsh which means very wet feet and the route through the dunes is completely random. The campsite and tramline tunnel are an interesting diversion but I wouldn't reccomend this walk to anyone in particular. It is probably more challanging for a mountain bike rider.
On the other side of Karekare is a much worthier bag. Follow Comans Track (now part of Sir Ed's Walkway) to the Mercer Bay cliff tops onto Hikurangi and back down to Karekare again. At 278m it is therefore a higher climb. With the cliffs over 200m you get much better views and a better track condition. Only downside is the houses at the top. If a few more of you try it, I can easily see it getting added to the possibles list.