Remember, it’s really the tar in cigarettes that is harmful, not the nicotine. The nicotine is simply addictive, but not as addictive as people like to pretend it is. As a former 2-pack/day smoker myself, I think I can fairly say I didn’t have much trouble quitting when I learned to challenge the assumptions behind my smoking habit. At that point, quitting became an existential decision.
@anartist – You can Google around for more, but here’s a summary article about potential health benefits of nicotine: http://health.howstuffworks.com/nicotine-health-benefits.htm
Most interesting is that it might have a positive effect on depression. Therefore, there’s a possibility that people suffering from depression are self-medicating themselves when they smoke. This might even explain why smoking is pleasurable for so many people in the first place.
(I’m always loathe to bring this point up because people get extremely sanctimonious about it. Keep in mind these things are possible developments that could someday yield useful results. )