ajobbins: I dropped 2D in favour of VF recently. When travelling around NZ I was constantly in and out of coverage, often with "Emergency Calls Only" when my wife had good coverage on Vodafone. The roaming, particularly in areas where 2D have some coverage but it's patchy is very problematic. In and around cities 2D was fine, but moving around it was a nightmare.
Rurally the amount of places where I have Spark but no 2degrees or Vodafone can be a bit disappointing, but not enough to make the effort of changing worthwhile.