I think the nic ratings must be approximations, and after that, differences occur with the aforementioned body chemistry originating from genetics, diet and hydration, medication, etc. Different people respond differently to different kinds of leaf. I can get light headed from nicotine, but sturdy burley blends don't often give me any sense of nic at all, or slight. I do look at the ratings and take it as fair warning. I usually start out with a high-rated leaf or blend in a small or partial bowl to see how it goes. I don't mind diving in, but I'm not always in a position to recover. I almost never buy a blend for a nic hit, but when it happens, I usually enjoy it, if it is not dizzying. I will say, I'm a moderate smoker, mostly a bowl or two a day, with days off. If you have much trouble, but enjoy a pipe, try various filters to see if that works for you. Many mild blends can be quite good, depending on your taste.