Hey MTB Dirters, back from NZ so I thought I would share my experiences with y'all. First up, Whakarewarewa Forest "The Redwoods" in Rotorvegas. Pics are a bit crappy, from mobile phone camera.
Taking my own bike was not an option, Bike Vegas on Fenton Street hooked me up with this:

Steel framed 29er Haro Mary 1x9. Flat bars, ridiculously large wheels and 9 gears....not the kind of bike I am used to, but it did the job no worries. $50NZ for the day.
The trail network is mammoth....over 100km's of signed MTB trails. Knew I only had one day, so couldn't ride everything I wanted. Rode most of the core centre trails, and climbed up to ride Roller Coaster and Hot X Bun....worth the trip. There was a shuttle available, but I am not a softie, so I rode all the hills to "earn my turns".

The thick tree canopy shades a lot of the trails within the core network. The terrain as a result is very grippy hard-packed soil...totally different to my native Gap Creek.

The walls of trees can be very dis-orienting. Invest in a trail map ($5 from most bike shops or Visitor Centre), or borrow a map from a jet-setting, Post Grad scholarship, potato fondling mate (thanks Stu). The tree canopy puts much of the trail surface in the dark, there was barely a cloud in the sky the day I did this ride, but inside the forest it was dark as. Photo-chromatic lenses for your glasses would be a huge bonus.
The forest is littered with these red Mushrooms. I resisted temptation to take a few up back to the Hotel and hope for some psychedelic affects.

The trails are really well signed, use the map to get your bearings and then follow the red signs to complete the trails. The trails are directional, mind you are not riding the wrong way up any trails.

Every trail is graded 1 through 5. I rode mostly Grade 3 trails and a couple of Grade 4's. Ride to your limits, I was by myself and walked some stuff I would have normally ridden, simply because I was in an unfamiliar spot. Mobile coverage in the forest was also a little bit sketchy in places. The trails are long....and many can be linked up to for a long flowing trail loop. I had only one bidon, which was sufficient as there are places to get water all around the Forest.
Redwoods is amazing place, I'm def going back next year with my own bike to ride. You would need 3-4 days to really do justice to the place, it is huge. I rode for about 6 hours all up, probs covered 50-60km including ride in and out of town. Plenty of carparking if you are driving.
Some general tips for anyone heading that way:
Take your bike if you can. The loaner was adequate, but all the time I was saying to myself "this would be so much better on my bike" etc. I didn't mind the 29er, but it was heavy as. I'd like to ride a decently specced one....maybe I need to have a word with a certain "bling obsessed" rider I see out at the Nundah crit track sometimes..
If you must hire a bike, take your saddle and pedals with you. I took my pedals, but was kicking myself at the end of the ride for not bringing my saddle also....damn WTB P.O.S.....ouch.
Rubber - loaner bike had 2.2 wire bead Kenda Nevegals...waaaaaaay too much tyre for the riding I was doing. If you will be XC'ing rather than hucking, 2.0 inch fast rolling treads with tubeless would be ideal.
"B Rude Not 2" and "Mad if U Don't" are must rides. They flow into each other for over 3km of great singletrack. "Roller Coaster" and the Pump Track are also another great fun. There is the World Cup DH course is in the centre of the park also...I gave that one a miss.
Go with a mate if possible, you'll feel safer and have more fun for sure.
Cheers.