Update from NZ —

2degrees never worked.
Phone defaulted to Spark, which wouldn't work on 2G.
Switched to Vodafone, which worked great on 2G (100 KBPS)
Later in the trip, I switched to Spark, and the 2G worked. Go figure.

Bottom line — when in NZ, change your default to Vodafone and start from there. Maybe someone could update the wiki.