Nicotine is not caffeine

E-cigarette enthusiasts are now routinely saying that the effects of nicotine are no more bothersome than caffeine (for example, Peter Hajeck and John Britton on BBC). 
 
They (and the media quoting them) should read Chapter 5 "Nicotine" of the 2014 Surgeon General's report.  Here are the conclusions:
 

1. The evidence is sufficient to infer that at high-enough doses nicotine has acute toxicity.

2. The evidence is sufficient to infer that nicotine activates multiple biological pathways through which smoking increases risk for disease.
 
3. The evidence is sufficient to infer that nicotine exposure during fetal development, a critical window for brain development, has lasting adverse consequences for brain development.
 
4. The evidence is sufficient to infer that nicotine adversely affects maternal and fetal health during pregnancy, contributing to multiple adverse outcomes such as preterm delivery and stillbirth.

5. The evidence is suggestive that nicotine exposure during adolescence, a critical window for brain development, may have lasting adverse consequences for
brain development.

6. The evidence is inadequate to infer the presence or absence of a causal relationship between exposure to nicotine and risk for cancer.

 
(The last conclusion only relates to the direct carcinogenic effects of nicotine.  Nicotine reacts with other chemicals to create tobacco specific nitrosamines, which are powerful carcinogens.)
 
They would also be well-served to read what the 1988 Surgeon General's report The Health Consequences of Smoking: Nicotine Addiction, said on this point because it addressed the caffeine-nicotine comparison directly:
 

Most categories of drugs which have been found to cause widespread drug dependence in the nonlaboratory setting have been tested with animals and humans in laboratory settings. Results of these studies have been reviewed in detail elsewhere  Several categories of drugs have been found to be self-administered by humans and animals in the laboratory settings, to meet criteria as positive reinforcers, and to exhibit orderly relations as a function of drug dose, drug pretreatment, and other factors known to affect the intake of dependence-producing drugs. These include alcohol, morphine, pentobarbital, amphetamine, cocaine, and nicotine in the forms of cigarettes and i.v. injection.
 
Self-administration studies with animals are much more extensive and have also been reviewed in detail elsewhere. In brief, drug self-administration studies in animals in the 1960s showed that a range of drugs including opioids, amphetamines, barbiturates, certain organic solvents, alcohol, cocaine, and nicotine were self-administered. All of these drugs were found to maintain powerful chains of drug-seeking behavior, even when insufficient drug was taken to produce a clinically significant degree of physical dependence. Drugs that did not serve as reinforcers in these studies included caffeine…” [emphasis added, citations deleted]