Default Aussie server is Europe? That's wierd because I defaulted to the US. You must of been jinxed and went to the evil, evil Euro server
Seriously though, I find it wierd you defaulted to europe - where did you buy GW? Online,? at EB? or some other store? I ask because I bought my copy at EB, got the Euro box insides but the server I defaulted to was America. Maybe they have changed thing's since I created my account...
My suggestion is that if your an english speaking aussie.. swap over to the American server's and live the good life

Seriously tho, I'd suggest doing it purely because A) there's more people on them & B) more english speakers on them & C) I've heard american server's have less lag than Euro server's.