I got here on one, and can testify that it is nowhere near as easy as everybody here says!
I decided to go this route when the point system changed, and as a medical professional with 14 years experience suddenly dropped enough points to no longer be eligible for a skilled migrant 175 to get here during one of the many criteria changes; emailed the minister for immigration via an open forum to ask how i could migrate to australia. The response I recieved advised me that sponsorship via work or state was preferred. This was in 2010.
Fortunately I found sponsorship, and now have pr through the 457 transition scheme.
I don't know anybody on a 457 who is flipping burgers, or doing unskilled work, and believe me I know a lot of people on 457's.