Quite frankly, you'd be hard-pressed to find a worse way to travel any great distance in Australia than on a bus. Busses tend to travel at night, so there's usually no view, the seats are comfortable, but hardly throne-like, and they're full people who can't afford a car, or the extra twenty dollars to get on a plane. Very few people would consider travelling between major Australian cities by bus (the airfares only cost a fraction more), but it is often the only real affordable option if you want to travel between small country towns, or see more remote scenery.
In fact, some of the most scenic countryside in Australia (like the Snowy Mountains and much of the West Australian coastline) is only accessible by road, so if your budget doesn't allow for multiple combinations of airfares and hire cars, a regional bus pass is a great way to see the country. Prices generally work out to be about 10c for every kilometre you travel.
Greyhound Australia offer a range of passes which are limited by the number of days and kilometres you can travel. You can view full details on their 'Aussie Explorer Pass' page. Prices start at about $113 for a three day, 1000km pass, and go up to $2573 for a 365 day All Australian Pass, which allows you to travel pretty much anywhere in the country, including about 50% of the coastline and all the major inland routes.
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