I got my copy yesterday and have had a bit of a look through. It's obviously very good and a noticeable improvement on all of the existing Australian guides. I've always been puzzled by people who claimed that there was no big need for an improved Australian field guide. The existing ones all had their strengths but all had significant flaws, certainly in comparison to the Collins guide. This book definitely provides something that's comparable to the Collins and Sibley guides.
On first impressions I'd agree that it's maybe not quite as good as the Collins. The illustrations, while very good, don't always seem quite as believable as most of the Collins ones. They sometimes seem a bit too clean and static looking - very slightly like they're pictures of stuffed birds rather than living ones (particularly the raptors). A few (particularly those by Jeff Davies) look a little bit anaemic, although the ones by Peter Marsack (most of the passerines) seem more saturated. The text seems good but I'd agree that it's not quite as efficient and to the ID point as the Collins. Sometimes they seem to get a bit carried away with the space they have and mention things that aren't that relevant e.g. the breeding habitat of vagrant North American waders. In the few cases I've compared against the Collins, it's not as comparative in the ID descriptions i.e. it doesn't say as much about how to distinguish species x from similar species y. It does do this, but could perhaps do it more in some cases.
There are some very good things though. An obvious thing is that they really seem to illustrate a lot of plumages and variations. For example, there are 14 illustrations for Long-tailed Skua, across a very wide range of plumages. There's also fairly liberal use of more impressionistic, 'jizzy', in-habitat illustrations of how birds might look in real life - something I like to see and that the Collins pioneered. These aren't as frequent as in the Collins but they're much more regularly used than in the Sibley.
It's also worth pointing out that this book isn't just useful for those birding in Australia. The treatment of Asiatic shorebirds might be the best in any current guide. If you're into seabirds you should also get this book. By my reckoning there 86 species of tubenose described and illustrated over 45 pages, in most cases with 5-10 illustrations per species. They also cover a few 'emerging' species in this group (e.g. 'New Caledonian Storm-Petrel'), which is nice to see.
Anyway, it's really good. Well done to all the people involved.