Hot water springs are definitely nicer during an Icelandic winter than during a heatwave in Australia's Northern Territory. Nevertheless, the Mataranka area makes for a very pleasant and unexpected visit, in a region where one is more used to the vastness of the desert than a turquoise water spring! I would therefore strongly recommend this area whilst staying in the region.
In fact, I have been quite surprised by the lush vegetation, with huge palm trees and lianas that give the impression that you have suddenly been plunged into the middle of the jungle. It's also worth mentioning that there are freshwater crocodiles in the springs, but they are harmless... It could be a tactic to scare off tourists and to keep this idyllic refuge just for the locals!