I suggest you use Impostah to get access to US catalog.
You need to do this without a SIM inserted, before activation, with access to WiFi and WOSQI.
I am on Optus, and have good 3G in cities.
OTA update to 2.2.3, or use the Dr.
If you have a TP as well, you can share apps.
There is nothing else special you need to worry about with the Pre3 in Oz.
I installed UberKernal and Govnah to manage battery life, but otherwise its standard and fast.
I have had Pre-, Pre2 and now Pre3, all no major probs with Optus.
One issue I do have, that I can't seem to find a solution to is 'Please check your "email_provider" Login and Password.' I need to reset the password nearly every day. I think its the POP/SMTP/SSL settings, but I can't find a combination that works.