I actually bought 4 different guide books to plan my trip Down Under. I ditched 3 of them almost immediately because Frommer's format was easier to read and locating appropriate information quicker. The advice on suggested tours was especially accurate; the boxed information warrants a second (or third) look - Frommer's never steered us in the wrong direction. Take the price information with a grain of salt as seasoned travelers know that pricing can and will fluctuate.
Don't buy any other guides - relax and enjoy your trip. Aussies are the most laid-back, patient crowd on the planet. It's an amazing country!
