jamesrobert: If you have paid upfront for the MySky (as I have), $18.70 a month is well worth it. You don't own the MySky so if it craps out, you get a new one at no cost. There is no extra HD fee for TVNZ and TV3 channels. An added bonus is 2 free Sky channels every month (some OK, some not).
Highly recommended, the MySky is still arguably the best PVR.
I'm in the same boat as you (as of yesterday). What's the deal with the 2 free Sky channels each month? This is the first I've heard of it. Ideally for me it'll be the kids channels for when my daughter just has to watch Mickey Mouse (which isn't on Netflix). I do find it odd that the TVNZ Kids channel is one of the Sky channels that are cut off.