Unlike most countries, Australia requires that all migration agents pass a university course in Immigration Law before they can be registered as migration agents. For their annual registration to be renewed, migration agents must attend professional development courses and maintain a professional library.
Furthermore the professional conduct of agents is monitored by MARA the independent professional body appointed to ensure that standards in the profession are maintained. You can be reassured therefore that MARA will protect your interests and ensure that the conduct of your agent is at all times professional and objective (and that for example, all client fees are held in a client trust account until an agreed event has occurred).
Finally, many visa classes are now handled by Immigration Department branches in Australia rather than in the various overseas posts (for example with the exception of Hong Kong and Taiwan, all overseas business visas are now processed in Perth, whilst all Skilled visas are dealt with in Adelaide). This means that an Australian migration agent is on the spot and will often be able to communicate with Immigration Department officers about a particular case.