In general, having international work experience looks good on any CV. Most companies in sydney are globally competitive and thus held in generally high regard.
You are lucky if you can do this by yourself ( at your inititive) PROVIDED your company supports you. You are also lucky that you will have a job once landed on the shores of sydney. This makes it so much easier than coming in anyother way.
The work-life may be a bit easier than the UK/US. However, sydney is fast approaching the helter-skelter demanding work environments as in the US/UK. This is just global competition at work.
The working environment is generally friendly and supportive.
Salaries in sydney are generally high ( and they have to be- sky high income tax and cost of living). Rents/buying a house is ridiculous. However, make sure you negotiate your salary.
Regarding family, australian cities are known for ease of family life ( for lack of better words)- you know what i mean- flexible workign conditions, understanding team and bosses etc...
Something that aint in the US/UK as much. Decent schools , etc...The main gripe i hear so often with any australian city is that its damn well impossible to save any money. The costs are just too high- and sydney is probably the worst offender in that regard.
If its money you are after, forget sydney - forget australia in fact. If its a balanced life you are after then there is few that match sydney ( or most australian city).