Revstar
Yes Australia is involved in a large trial of ADS-B but its NOT a radar replacement. Its going to replace their procedural service, so there is no correlation between radar and ADS-B in the Australian model.
I think the biggest 'problem' with ADS-B (and I really like the concept from an ATSP perspective) is that it would require a mandate for every aircraft to be equipped. That gives an issue for the GA fraternity but more than that is the probability that the military will fight it very hard. They're already exempt from RVSM regulations and ADS-B gives a lot more data!
BD