I think the severity of the addiction varies from person to person. If you are really addicted to nicotine, yes, the withdrawal can be crippling. With some people, the nicotine affects every thing someone does in a day--from regulating sleeping patterns, digestive functions, appetite, (obviously) mood, vision, even the way that person moves and thinks. You can get the same kind of misery brought on by heroin withdrawal (chills, cold sweats, nausea, shakiness, muscle/bone pain, fever, etc.)
Of course, that doesn't happen with everyone. I only know two people who had severe withdrawal like mentioned above after quitting cold turkey. Most people I know just get really moody and annoying when they try to quit (cold turkey or otherwise.) I haven't had a cigarette in... like... a week or two? I don't really notice any difference... but I'm also not really "addicted", I guess I'm classified as a "social smoker".
I guess my point is: just because I don't get a nasty withdrawal doesn't mean that I think every other person out there is just being melodramatic when they nic-fit. Besides, why would doctors lie about something's addiction potential if it's legal? I mean, I can understand being skeptical about a doctor berating someone about the dangers of an illegal substance, assuming most of it is propaganda. There are doctors that preach that kind of stuff... but nicotine addiction is kind of a gold mine in the US anyway.