One thing to be aware of the price of the books are going to be more expensive for International users. Because they haven't actually entered in to any international agreements for the data, they've just partnered with AT&T, so you pay the cost of international roaming. So it may still be cheaper than paying international shipping fees but they will be more expensive than the prices you're seeing.
From The Guardian
When asked by the Guardian precisely how much downloads would cost, an Amazon.co.uk spokesman revealed that foreign customers - including those in Britain - would be paying $13.99 (£8.75) per book instead of the American price of $9.99 (£6.25). That amounts to a 40% premium for the same title.
...
Providing the wireless download service had proven a sticking point in the company's attempt to launch the Kindle outside America, after the retailer failed to come to an agreement with various mobile phone networks around the world. To push through the launch, the company instead chose to partner with American phone company AT&T, which already has its own international roaming deals around the world - including with British networks O2, Vodafone, Orange and 3.
The cost of receiving data over these roaming connections is notoriously high, however, with AT&T's ordinary mobile phone customers who use the service outside the United States paying just over a penny for each kilobyte of data they download. That means that an average book download would cost the equivalent of £14.39 if sent to a mobile phone.
It is not only customers in Britain and other non-US countries who will be paying extra for their Kindle purchases, however. American customers who take their Kindles outside the United States will have to pay a $2 surcharge on every download - putting the price at $11.98 (£7.49). That is still lower than the international price, however.
At first I thought that this wasgoing to make a difference but I checked and the books I have been checking out are they are already listed at the Australian prices for me. If I had had to add to those prices I would have said NO WAY. The Australia price of a book that is $9.99 in the US is $11.99.