Pretty simple and can't be bothered looking at all the reviews and I know i'll get a quick answer here :)
This is the NZ partpicker list http://nz.pcpartpicker.com/parts/thermal-paste/
price isn't a problem really, it's only a couple of bucks, but I don;t just want the most expensive one unless it's a good few degrees better than others.
noctua nth1. I only ever use that or mx-4 these days. They'll all pretty much the same, ive even used zinc oxide (the stuff you can use as a sunscreen), works just fine as well. Though I wouldnt recommend it for long term use, it may degrade quick..
Arctic Silver 5 is an oldie by goodie. It has about a 200 hour cure/burn-in time, and is electrically capacitive. A lot people still recommend it, but others have moved onto newer things that are non-capacitive, with minimul-or-no cure time. (Arctic Silver Ceramique 2 is the "updated" Arctic Silver 5.)
I personally use Arctic Cooling MX-4, but Noctua NT-H1 is great as well. Honestly, with brand name thermal compounds, most operate within a couple degrees of one-another, so it's not worth splitting hairs. Pick one, and be happy. :)
I used Arctic Silver 5 before, I hate it. Using it on a Hyper 212 EVO, I hate it. The thing slides across the CPU like oil. I'd rather use something that just sticks in place for a better seal/contact. I use IC Diamond 24K (only difference between 7K is more thermal paste in a bottle.) LinusTechTips uses IC Diamond too because he says as an overclocker he hasn't had anything else that produced consistant temperatures.
A lot of people say it can rub away the lettering on the IHS (Integrated Heat Sink or Heat Spreader); however, I don't find this to be true, plus on there website they have the most documentation for any thermal paste I have ever seen.
http://www.amazon.com/IC-Diamond-Carat-Thermal-Compound/dp/B0042IBAOG 24K Version
http://www.amazon.com/Innovation-Cooling-Diamond-Thermal-Compound/dp/B0042IEVD8/ 7K Version
http://www.innovationcooling.com/ There website where you can see a TON of documentation on the product, including a *average* temperature drop for over 700 systems they found in forums like tomshardware.
I use AS5. Never have had any issues with it. Used it on all my PC builds as well as on an overheating Xbox 360. Works great. I have never noticed or paid much attention to that 200 hour "curing time." Never noticed much change in performance.
And that depends on the application of said paste ... on GPUs I would not use an electrically conductive paste ... but for CPUs asw long as you are careful not to let it ooze out the sides ... it is not as important
I believe for most thermal pastes, there's something like a "set-in" time. When first applied, the performance isn't bad, but isn't great. As time passes on, the thermal compound kind of sets in/cures and conducts heat better.
Non-conductive is sometimes slightly less efficient than conductive thermal paste, but being non-conductive means that you can apply it to more things with less risk of harm. For example, if you wanted to repaste your GPU's die, using a non-conductive paste would reduce the risk of accidentally shorting out some tiny resistor on the GPU than if you used conductive thermal paste.