I'm also Australian, and cannot watch 720p60 on Twitch. 16mbps downstream over ADSL2+ in Melbourne.
720p60 is fine on YouTube. 1080p60 on YouTube will stutter depending on what my girlfriend is doing on the Internet, but is watchable if I'm home alone.
Anything over 720p60 won't even try to start playing on Twitch.
I'm one of the Lucky Few who have real NBN (100mbit down). YouTube 1080p60 is fine, but Twitch and Mixer seem to be coming from Hong Kong and stutter / drop out.
720p60 is fine on YouTube. 1080p60 on YouTube will stutter depending on what my girlfriend is doing on the Internet, but is watchable if I'm home alone.
Anything over 720p60 won't even try to start playing on Twitch.