The seventh edition of the Lonely Planet "Sydney - City Guide" was researched and written by Sandra Bao, with help from the author of the previous two editions Sally O'Brien. This edition was published in 2006, which means that the next edition will probably not be published until sometime in 2008 or later.
As with the other City Guides from Lonely Planet that I have used, this one appears to be comprehensive. As one would expect, it would cover the things that most travel guides cover, such as lodging, food & drink, entertainment & attractions, and shopping. The Lonely Planet guides go beyond the standard information and include sections on city life, art, architecture, and history, and sections which help the traveler plan activities with sections on walking tours, and excursions that can be taken outside of the city.
This guide, like the other Lonely Planet guides that I have used, has been very helpful in my planning for my visit. Probably the most useful section to a first time traveler is the `Directory' section, which covers a wide range of topics from transportation, family concerns, climate, customs, information for travelers which are disabled, electricity, embassies, emergencies, and so much more. If you already have a Lonely Planet guide for Australia, then this section will not be of as much use, but it is always good to have the latest copy you can because some of the information changes or is added.
I have had very good success with the Lonely Planet guides, and I have every reason to believe after reading and using this one for my planning that this one will also turn out to be quite useful. There are guides which give you more visual information on Sydney, but in terms of written content I believe this one is near the top of the list.