At the risk of getting off-topic, here are some options to help you reality-check your best 3G broadband deal (e.g. prepaid 3G modem w. 1G or similar usage):
- whirlpool.net.au forums: wireless ISPs
- Ozbargain.com.au (in case there is a great deal; just search '3G' or a similar term)

The former is overkill for casual users but useful if you want to find details debated.
The latter found a Vodafone modem for A$59 with 1Gb data. More useful for locals but worth a check if you've time and the inclination.

In addition to McDs, be aware of a wireless company Unwired. It's owned by a major public company and has free wireless access at some cafes and most libraries (at least that's my experience in Sydney). These managed wifi hotspots are free to use (usually ~7AM-7PM).

Good to know; just check with this link: Store Finder and you get a Google Map with the location of each free wifi hotspot - without some of the McD restrictions.

Cheers,
BB