Originally Posted by davidweb

The country specific domains like .com.au/.co.uk receive ranking benefits in their respective countries like Australia, and UK.

It is upto you to decide whether your business is confined to Australia or worldwide ( maybe after 1-2 years).

Your immediate SEO efforts will help you gain quick rankings on Google.com.au ( since you have a .com.au domain). However if your target is worldwide, then having a .com domain would be a better choice, but there are no fixed rules.

Even a .com.au or .co.uk domain can capture top rankings on Google.com ( US or worldwide) depending upon variety of SEO factors.

On the other hand if you own a .com domain, then having a country specific hosting/I.P Address can help your website to gain higher rankings within Australia (ninemsn.com.au Yahoo!7 google.com.au).

You can read similar case studies at : Google Geographic Targeting » SEO HAWK