The slow-carb diet is an excellent diet for weight loss and does avoid some of the problems of other rapid weight loss diets; it controls calorie intake without forcing you to count calories. I counted calories for the first week or so I was on it (in vegetarian form, which is a little bit of a challenge, to get enough protein without resorting to soy and wheat gluten products), and found I was eating about 200-300 below my resting metabolic rate every day, while eating enough to never feel hungry or get snacky. There's no way I could avoid losing weight if I'm eating significantly fewer calories than what I burn just sitting at my desk, and there is pretty solid science that the ingredients in the diet encourage loss of fat rather than loss of muscle...you're getting plenty of the stuff you need to maintain muscle mass, and adding some things to increase burning of fat for fuel.
As an aside, I've found the easily testable bits (particularly the "boost testosterone and libido" chapter) to have very evident results. That may be just because I was deficient in a few of the vital nutrients, and returning to nominal made things better, but I definitely saw a change. I plan to keep Brazil nuts in the house at all times, henceforth, regardless.