keto breath - it tastes pretty bad, but not so much to other people
ammonia-like body odor - this was minor
lethargy - I operate better on carbs, and I was deep in ketosis, too. I didn't adapt to ketosis and somehow start feeling euphoric. I was a computer programmer and a student of computer science taking 18 credits, so it was especially hard.
carb-up - I did it too long, and ended up not meeting my goals. I should have done 24 hour carb-ups.
I think it is worth it. If I do it again, I will integrate it into a larger diet plan, perhaps doing an isocaloric diet before and after the CKD. I also think that a thermogenic is very helpful on this diet. It helps you to forget your body's yearning for carbs and have better workouts. If your main goal is weight-loss, try doing a depletion workout very early in the morning. Carb up the rest of the day. This will give you time to burn fat the night before, and will clear the fat out of your system for the carb-up.
You may gain weight the first week due to glycogen supercompensation. I read this, it happened to me, and to a friend that tried the diet. I follewed the plan in BodyOpus, except that I later switched to a Saturday morning depletion workout.