Buying a mobile phone from overseas

I am in the market for a new mobile phone (cell phones).  IPhone is out of the question as I don't like the closed and restrictive environment in which Apple likes to operate.  Windows 7 is too little, too late from a company who had a decent phone operating system and had neglected it for several years.  Microsoft has stopped innovating long time ago.

That leaves Android.  Google has kept updating and improving Android, and is committed to being an important player in the smart phone market.  I expect Google to keep updating Android fairly frequently, making sure to keep the operating system current and relevant.  Kind of the opposite of Microsoft.

As such, I am looking for a phone that will run Android.  That leaves me with a large selection to chose from.  HTC, Samsung, Motorola, LG and SonyEricsson make the majority of Android phones that are available in the market.

Buying phones, as well as anything else, in Australia is a bit more expensive than shopping anywhere else.  I am considering buying a phone from the USA or the UK and getting the phone shipped to me.  Not all phones are available for purchase in Australia, so being able to buy a phone overseas helps keep the price affordable.

Before I decide to import a phone into Australia, I need to confirm that the phone will work on the local frequencies.  All mobile phones in the world work on either GSM or CDMA systems for voice.  Majority of the networks in the world run on GSM, but not all phones are designed for it.  Australia runs only GSM networks, so I have to look for a GSM phone.

The next thing to watch out for are the frequencies that GSM phones operate on.  Here in Australia, the three major companies that run mobile networks are Telstra, Optus and Vodafone.  I will most likely be using my phone on the Optus network, but it would be good if my phone would support the other two networks in case I need to switch providers.
I need to check operating frequencies for all three networks.  At the same time, I need to confirm which frequencies they use for voice calls and which frequencies are used for data.

Technology	Telstra	OPTUS	Vodafone
2G	900/1800 MHz	900/1800 MHz	900/1800 MHz
3G	850/2100 MHz	900/2100 MHz	2100 MHz

Judging from the information above, I my new mobile phone should support GSM 900/1800 MHz for voice service, and at least 900/2100 MHz for 3G.  Telstra is the only one currently using 850 MHz for 3G service.

Reference: Mobile World Live