It's not too bad. There are a couple of pipes and routes, not all go through Telstra. I usually get about 225 ms pings between west coast Aust to west coast US (~9,500 miles). It's fine for regular internet including downloads, but gamers don't like it (I guess much of that latency is just down to plain old distance rather than bandwidth).
http://afr.com/p/technology/wozniak_likes_nbn_so_much_he_app...