it seems pretty dumb to me that they are going to build the Western Sydney Airport without a rail link for the first 5 or so years.
Not sure what airlines are going to use the new runways, but it will be a nightmare to get out there for all but those who live in the south west.
If they were smart they would build a high speed dedicated line that splits to CBD, Hurstville, Parramatta and Chatswood.
They should take serious look at Hong Kong's set up. There you can check-in at their Central Station (There are actually 6 locations on HK Island and Kowloon that you can drop off your bags), leave your bags with the airline, and then go get lunch or do some shopping. When it's time to leave, you jump on the airport express and zip @ 130km/h out to the airport. With no bags to worry about, you then just need to clear immigration and jump on your plane.