They basically only take care of the administrative things (ie. collecting your documents, sent them to Australia etc) and DO NOT have any effect on the decision Australian goverment to grant you visa or make it faster.
However, if you decide to use an agent, make sure they are registered with the Australian MARA (Migration Agent Registration Authority) or else you risk being fleeced by dodgy agent.
You DO NOT have to use any migration agent.
They basically only take care of the administrative things (ie. collecting your documents, sent them to Australia etc) and DO NOT have any effect on the decision Australian goverment to grant you visa or make it faster.
However, if you decide to use an agent, make sure they are registered with the Australian MARA (Migration Agent Registration Authority) or else you risk being fleeced by dodgy agent.
Worth take a look at the IMMI website below.
http://www.immi.gov.au/migrants/
Cheers
SK