As a former smoker, I can chime in here. I smoked for ~12 years and quit smoking ~12 years ago. Nicotine is (to my understanding) the only substance with the capacity to selectively flip a person's state. By this I mean that if a smoker is edgy or tense, smoking has a calming effect. If the smoker is tired or sleepy, smoking increases alertness. This is an important part of its addictiveness-- the power to regulate one's physical being. You can choose to be soothed or made alert.
On a more personal level, I do miss smoking on occasion but it's a mere faint echo of the powerful craving that you feel when you NEED a smoke. Smoking is most enjoyable after meals and when drinking alcohol. I used to use my smoke breaks to think and solved any number of work related problems while wandering around outside. Now, I just get up and walk around when I need a break from the office.