Driving in Australia pros:

Easy if you've driven in the UK.
Great cars -- Fords and Holdens (GMs) you'll never see in the States.
Well-kept roads, not much traffic outside the big CBDs.

Driving in Australia cons:

Distances are vast.
Price of petrol.
Speed traps. You'll soon see why Australian drivers appear so meek and compliant about speed limits.
Signage not always as profuse as one might like -- bring a good map.
Roads can be boring, and there's nothing -- nothing -- between towns.

In all honestly, if you want to get from Sydney to Cairns, etc., you'll find it just as cheap and twenty times as fast to fly than to drive. The trains seem very erratic, thin and intermittent.