OK So somethings have been glossed over in both the coverage and also peoples responses to this.
First of all, Steam currently sells games to Australians with regional pricing, which means they are basically an Australian store, which means they should damn well be including GST like every other Australian store they compete with (You already pay GST at EB/JB/etc). We are not treated the same as US customers, Doom is 80 USD for Australians for example.
Secondly I really hope a switch to treating Australia like a real region and paying taxes properly means we can move away from paying in USD here, with the way most banks and credit cards work this usually means you pay an extra 10+% in poor currency conversion rates and also bank fees (Less with specialized CC's of course, which I use and suggest to anyone who travels).
Third if you ever turned over more than 75k/year in sales to Australians you should already be registered for and paying GST according to the ATO, you also needed to be registered for GST if you ever received a federal grant which I did, so this actually evens things up between who played it safe and registered and those who thought GST didn't apply to them.
I'm not saying it won't suck if prices go up, though we really won't know if that's the case until closer to the day the switch happens, all I'm saying is that an Australian store (Which Steam undeniable is since it knows who its Australian customers are and gives them regional pricing) should definitely include GST.