The work is either poorly paid in relation to he extremely high cost of living or it's industrial work on the mines - which means living and working away in tough conditions.
Sydney, Brisbane, Melbourne and Perth are often considered the cities to offer a great lifestyle, but the reality is that unless you are a reasonably high, two income household then getting on the property ladder or living in a half-decent area is way beyond the budget of someone on a scaffolders wage.
People talk about going to the beach after work and stuff. Yes you can do that, but believe me, that gets boring after a while.
Pubs are very, very expensive. Forget going out with your work mates on a Friday night and getting hammered - most scaffs can't afford it. That is the reality.
There is also poor infrastructure on the housing estates, so forget having local pubs around the corner from your house. You might be lucky if there is a milk bar within 10 minutes walk.
The weather is overrated (although far better than the uk). It can get very cold in the winter down south. The television is appalling, they have the same social and economic problems that everyone else does and house prices are extremely high in areas where you're likely to find scaffolding work. Nobody goes out in the week - so believe me, a cold winters day in Sydney with neighbours on the telly at 19.00 can be very depressing.
I lived and worked there for 2 years, my brother lives there, I visit every year and have visited every state and territory (yes, including Tasmania) so dont jump down my throat if you disagree with me! It is a great country, but it ain't the utopia that some people believe it to be.
Oh yeah, and Adelaide is probably the most boring city in the world.
Good luck.