Well, I must have misunderstood something. I just received my copy of Pizzey & Knight, and it says "Reprinted 2002". It does not give an actual edition number, but it seems that the last update was in 2001. So my reference to a "new edition" was wrong. Sorry about that.
Now for the book: I agree that it is too large to take to the field. Just OK to have in the car or at home. That is a shame. The book is in the same size league as the original Sibley guide for North America.
I have no immediate plans to visit Australia. Rather, I bought the book for its allegedly superb illustrations. Now, I can't comment on their accuracy, but I am rather disappointed about their variable quality. One would certainly not think that all the plates were done by the same artist. Just compare pages 115 and 117, for example. Overall, on some plates the birds seem to come alive, whereas on others they are very two-dimensional. I.e. they appear very flat. Some birds like the lesser noddy appear overly slim. And, while some bird pictures are rather smallish, there are some that are rather too large. The storm-petrels on page 93 are a case in point, giving the plate a crowded appearance. But those drawings are otherwise of superb quality.
I emphasise these differences of the plates because there is usually considerable criticism when a new field guide comes out that has its plates done by several artists. Here, we find similar differences within the work done by the same artist. It is clear that doing all the artwork for such a book is a monumental task. And even a good artist is not always equally disposed, I would assume. And then, there is probably the pressure of a publishing schedule. However, what counts in the end are the pictures we all have to look at and work with for years. Thus, spreading the task does not seem to be such a bad way to do it, after all. That is, as long as you have several good artists with the available time. But it also means that it is a sensible solution to use the same good illustrations for several books, as has recently been done in the field guide to the Birds of Africa South of the Sahara.
One thing that keeps puzzling me - not only with respect to this field guide - is the fact that there is contents included that does not help in the field at all. Thus, we find here a lengthy chapter called "family introductions", the kind of info one would expect in an "encyclopaedia" type book. Also, what good is a long literature list in a field guide?