Cinnamon toast crunch is the best cereal by a long shot and I can guarantee this by asking anyone and everyone if it was a part of their childhood, and even adulthood. It is, without fail, the cereal I see the most people purchase when I am at the grocery store. We knew that if we were going to attempt a low carb cereal we would need to pick one that everyone could undoubtedly agree upon as the best, so we decided on Cinnamon Toast Crunch.
Most low-carb diet authors don't recommend bothering with it. Even many of those who think a ketogenic diet is a good thing just assume that a very-low-carbohydrate diet (under about 50 net grams of carbohydrate) is ketogenic. On the other hand, many people have found that monitoring their ketones, at least for a while, provides valuable information.