As another commenter alluded to I was referring to the crash or hangover.

As for withdrawal I don't think I have ever felt it with nicotine but it might be because I just don't ever do enough (the most pieces of gum I have had in one day is 40mg of nicotine.. ie 10 pieces). I have had a nicotine hangover with cigars but this is usually because alcohol is involved as well as I believe cigars lower intake of oxygen (just a theory.. probably wrong).

Caffeine withdrawal is awful.. absolutely awful for me. Headaches for days. I usually give up and pound 4 ibuprofen with a large cup of coffee.

Caffeine withdrawal, out of the many types, is my least favorite to experience.

Nicotine withdrawal (non-tobacco) is nearly unnoticeable, while nicbacco withdrawal can be a little annoying. Although, while I smoked for years, I never smoked more than a pack or two pipes full a week, so perhaps it scales.

Neither compares to the full on pounding headaches, teeth grinding, and occasional auditory hallucinations that can accompany cold turkey, n pots a day caffeine withdrawal.

I rate caffeine easily on par with opiates in terms of the length and discomfort of their withdrawal.

I think that @agentgt was talking about "coming down" from the high (or effects of the drug), and not withdrawal symptoms.