New Zealand is quite nice, and definitely worth a visit, even given the long ride. I have only been to NZ a couple of times from the States (East Coast), but have often gone down there for long weekends from Bangkok, where I try to explore regions less touristy on both the N and S Islands. You might want to consider adding a few more stops to your itinerary, time permitting, given that the marginal cost is relatively low to add stops in the south Pacific, Australia, or even SE Asia.

As far as jet lag goes, the posters above gives good advice regarding prescription hypnotics. My own favorites are Ambien (zolpidem tartrate) and Halcion (triazolam), with the former being the most effective and benign, with Halcion running a close second, at least IME.
Well, last time I looked, 12 time zones away from the east coast covers the entire planet, so if the question is whether there is anything on earth worth a day's discomfort in travel, I think the answer is obvious.