GoT is absolutely huge in Australia - I am continually surprised at the people I know who are well outside the target demographic and watch it. Monday is Game of Thrones night, where everyone watches it, and then talks about it with their mates, which seems to be a significant part of the experience (I'm not a fan of the show personally).
A week later is one week too late - you need to be looking at hours after screening. Australia has a huge pirated TV culture because of how awful our free to air is (pay TV is only really starting to catch on due to exclusive sports licenses, and in terms of getting US content it is almost as terrible as free to air), and everyone just torrents what they want to watch.
Guess we'll find out next week if it's the screening time because season 2 just finished. So from next Monday will there be a drop in Australian GoT torrents because the show is equally available on iTunes? It'd be interesting to see the stats.
The other thing is that on iiNet (Australia's #2 ISP), iTunes downloads aren't counted against download quota. So there's some incentive to buy for people on the basic plans.
A week later is one week too late - you need to be looking at hours after screening. Australia has a huge pirated TV culture because of how awful our free to air is (pay TV is only really starting to catch on due to exclusive sports licenses, and in terms of getting US content it is almost as terrible as free to air), and everyone just torrents what they want to watch.