I have used S&D for several years, spending weeks, and sometimes months, in the outback etc.. The book stays with my vehicle, and is used to check my identification of species when I return to my camp.
If you can't identify a species using this book you probably won't identify it at all.
Having been brought up on Troughton's "What Bird Is That", and having for many early years to try and identify birds using the not too good, tiny pictures, I am very happy to be able to use any of the now available field guides, all of which are a great help at times.
I now use S&D and am happy to continue using it; it is easy and quick to find what I am looking for, although now and then I have filmed birds that I have not yet identified, and not been able to find in any book.