Dan Margulis knows a lot about Photoshop, but his opinions on color management and the advantages of 16-bit editing are not based on practical reality or a solid understanding of the subject matter. Andrew Rodney, Bruce Fraser, and Ethan Hansen are far more knowledgeable and credible in those areas than Dan Margulis
I had looked at Professional Photoshop but decided not to buy it, since it emphasized CYMK, which I do not use. I see Dan has a new book on editing with LAB and this is on the bestseller lists.
Andrew and Bruce have stated that this space (LAB) is not the most intuitive space to work in and I'm not sure if I want to suffer the learning curve needed to give it a try. What do you think about LAB editing?