Won't bore you with the details but a few thoughts (can only speak to Welly).
As a Scottish-American with experience on both sides of the Atlantic, I'd say the culture here is more akin to the West Coast of the US than Britain - more Oregon than Manhattan Beach. They are pretty liberal with a leavening of entrepreneurial frontiersman-got-to-go-out-and-do-things-for-yourself. For prospective British migrants who are looking forward to going to Britain twenty years ago I'd say, don't think that. NZ is its own place.
NZ tends to adopt technology slowly then very fast in a big jump. Online banking is superb. Broadband still crappy but getting there. Do yourself a favor and forget the just awful terrestrial TV and get yourself a virtual US or UK IP address and do Amazon or Netflix instead.
I don't know about the experiences in the anti-NZ sites but I've found New Zealanders to be incredibly helpful and friendly. It's really helped having kids but I've been astonished how fast I've put down roots here. But you have to chip in. Scouts are unisex and have been fantastic and they get to do loads of interesting things (they even have their own flight school). Play parks are so much better here.
If you are going to dress up in fancy dress or get your kids dressed up, do it well. They are seriously into this here. The World of Wearable Art is the prime example and is a must to visit at least once in your life. So are the Sevens if only for the cycling men in mankinis. They are probably senior civil servants.
Everyone is doing something else after work. Either tending to their bees, cycling, sailing, running a business on the side, growing veggies, kayaking...you name it. The commute is so good you can get home in the summer and really enjoy yourself.
Yes the food is expensive and yes the best way to overcome that is go Kiwi - buy food on special and use local providers or catch it or grow it yourself. Yes the pay isn't that good but is defo made up for in quality of life. Yes it's windy in Welly but when it's not it is a paradise. Yes it's far away and you can't get over that. Yes dentists cost the Earth. If you have a lot to do, consider going to Thailand. Only thing I would really fault NZ over is that one of its greatest strengths is its greatest weakness. NZ is the home of second chances and fresh starts. But it also means that Ponzi perps like David Ross (think Bernie Madoff of the South) only get the equivalent of a slap on the wrist for ruining peoples' lives.
Was it worth coming here? Abson-toot-ly.