My progress has been gradual and I've never had the dramatic loss of appetite that the book describes. I am concerned that people drop off the plan too quickly when they find that they still have an appetite. They may think it's not working. It's hard to notice a difference in eating of a few hundred calories a day until the deficit accumulates for several weeks, but some people are not patient.
I think this is the biggest concern with any diet. People tend to become easily discouraged and give up when any kind of plateau or slowdown starts to occur. People tend to have innaccurate ideas of how fast you can/should lose weight. People misunderstand that weight does not equal fat, so if you are lifting weights or exercising your weight could be edging up even though your fat level is dropping. Like most things in the human condition, it is more complicated than it initially seems.
The real reason people give up at plateaus is that in a classical diet, once you hit the plateau, you've hit the failure stage. A classic diet works because you are changing the flavors and types of food you are eating. When the change wears off, then you plateau. Then the yo-yo kicks in and you are in full fledged failure.
In this method, a plateau is just a plateau. I've lost about 63 pounds (down another half pound this morning). The last forty pounds lost, about half of the time in the last five months (I've been on seven months today) has been spent on plateaus.
I was kind of depressed at the start of this week, another 3-4 days of a plateau, when I realized that I'd lost almost ten pounds in the last month (actually ten pounds in 33 days). While my weight loss has varied, from 15 to 5 pounds a month, it is usually about eight pounds a month. The plateaus cause me to lose sight of that, which is why keeping a record is so important to me.
But, plateaus don't mean failure in the Shangri-la diet. Often they seem to be just water retention, as people often lose belt sizes during them (I did on the last plateau, which was strange).
Also, it is important to realize that many people lose 2-3 pounds a month on the diet, so a little bit of fluctuation or water retention can mask a lot. A pint of water, two cups, is one pound.
Keep it up.