Nicotine get 9 out of 10 people addicted to it, heroin only does like 1 in 8. Nicotine also kills about 450,000 people per year while heroin only kills a few thousand and that's mostly because it's illegal and has no quality control. Nicotine is the true heavy-weight of the drug world.
Quit no matter what, it's worth all the crap to do it.