I was looking at some hostels from this site, basically these 3 all look good, anyone been there?
They all seem to be modern, centrally located and claim to be clean. I'd say cleanliness is the most important factor for me.
Also wondering what booking is like around New year's, I know places like Sydney get booked early, but what about Auckland, should I be booking now? I probably will book it soon anyway...
The Base is on a pretty dodgy street (I know cause I stayed at a hostel a couple of buildings down the road for a while) - although Auckland's concept of dodgy is still quite acceptable. Usually Bases are very modern and clean, although they're too party-oriented for my tastes.
There's two YHA's in Auckland: The first is the YHA International, which has awesome super-modern facilities, but has plastic pillows and often smells funny, and also boasts an industrial strength kitchen which only has a negative point in that it gets really warm during the summer due to the massive windows. The second is the YHA City, just up the hill from the International one, which has noticeably older facilities, but feels much cozier, and has a pretty great in-house eatery, which is just awesome when you need something extra for breakfast.
I've stayed frequently at both, and will happily recommend them, despite their faults.
I think you should be fine with booking Auckland up to two weeks in advance or so, although if you know you'll be going anyway, there's no harm in booking earlier.
Try the Budget Backpackers Hostels (BBH) website (bbh.co.nz). They have loads of hostels on there including a description and a rating given by people who have stayed there in the past.