Since I've now completed the trip (or at least the NZ-operated legs of it), I thought I'd leave my own thoughts behind for posterity in case anyone has the same question in the future.

The flights I took with NZ and aircraft operating were:
YVR-AKL (77E)
AKL-MEL (77W)
SYD-AKL (763)
AKL-SFO (77W)
AKL-ZQN-AKL (320)

Overall, I'd say I was quite happy with NZ's service. I usually don't mind AC's long-haul J service, so I'm not one of those guys who will just dump on AC for the sake of it, but NZ was consistently better all around.

AKL-SFO is on the 777-200ER. The 200s' interiors are being upgraded to the same standard as the 300s (more on that below) throughout 2015, so YMMV. I had the old design. Still slightly better than AC. They give you a small mattress and a couple of decent sized pillows that actually make it feel like a bed, completely unlike AC's lie-flat seat and sorry excuse for a pillow. It also feels like it's slightly longer.

The pod is similar in layout and dimensions to AC's, but just all around better. Better places to store things, IFE locks into the wall with screen facing out so it's not fully away for take-off/landing. A more liveable space, really. A lot of incremental improvements that I'd say add up to an all-around much better product than AC's.

The pod on the 77W is pretty similar but just newer and nicer. Again, clear winner over AC.

The food was really good. Honest-to-god enjoyable food. The ice cream I had for dessert on YVR-AKL and the beef salad main course on SYD-AKL were food that I would actually have been pleased with in a good restaurant. Most of AC's catering I find okay, but I've never had anything (other than maybe the cookies + ice cream) that I'd ever want to eat again outside of a plane. NZ did deliver that with a few dishes (not all were as good, but none were bad).

Crews were friendly and attentive throughout all flights. On long-hauls in J, I'd generally say the same about AC crew, but NZ's were still probably slightly better.

IFE, I didn't notice a huge difference. Slightly less laggy and slightly larger selection, but I've never had that many problems with IFE, so maybe a slight win for NZ here, but not much.

Overall, I was very, very pleased and would definitely fly NZ again if I needed to be in that neck of the woods.

That being said, NZ isn't perfect. OLCI didn't work (about 50% of their itineraries aren't eligible - but of course when you try to check in it doesn't say you're not elgible, it tells you OLCI isn't open yet, or is already closed). Had some issues getting the flights all ticketed correctly and bags checked through and BPs at various points. In some cases worse than dealing with AC. There's also some negative feedback on the NZ FT about how NZ is cheapening their product and so on.

But given the choice, NZ is a clear winner to me.