Many of you have already seen Gwern's page on the topic of nicotine use. Nicotine is interesting because it's a stimulant, it may increase intelligence (I believe Daniel Kahneman said he was smarter back when he used to smoke), and it may be useful for habit formation.

However, the Cleveland Clinic thinks they put your heart at risk. This site covers some of the same research, and counterpoint is offered:

Elaine Keller, president of the CASAA, pointed to other recently published research that she said shows outcomes in the “real world” as opposed to a laboratory. One study showed that smokers put on nicotine replacement therapy after suffering an acute coronary event like a heart attack or stroke had no greater risk of a second incident within one year than those who were not.

I managed to get ahold of the study in question, and it seems to me that it damns e-cigarettes by faint praise. Based on a quick skim, researchers studied smokers who recently suffered an acute coronary syndrome (ACS). The treatment group was given e-cigarettes for nicotine replacement therapy, while the control group was left alone. Given that baseline success rates in quitting smoking are on the order of 10-20%, it seems safe to say that the control group mostly continued smoking as they had previously. (The study authors say "tobacco use during follow-up could not be accurately assessed because of the variability in documentation and, therefore, was not included in the present analysis", so we are left guessing.)

29% of the nicotine replacement group suffered an adverse event in the year following the intervention, and 31% of the control group did--similar numbers. So one interpretation of this study is that if you are a smoker in your fifties and you have already experienced an acute coronary syndrome, switching from cigarettes to e-cigs will do little to help you avoid further health issues in the next year. Doesn't exactly inspire confidence.

Another more recent article states that older smokers should see health gains from quitting cigarettes, which hammers the nail in further for e-cigarettes. It also states:

More conclusive answers about how e-cigarettes affect the body long-term are forthcoming, Rose said. Millions in research dollars are being funneled toward this topic.

“There is some poor science,” Rose said. “Everybody is trying to get something out quick in order to get funding.”

So based on this very cursory analysis I'm inclined to hold off until more research comes in. But these are just a few data points--I haven't read this government review which claims "e-cigarettes are about 95% less harmful than tobacco cigarettes", for example.

The broad issue I see is that most e-cigarette literature is focused on whether switching from cigarettes to e-cigarettes is a good idea, not whether using e-cigarettes as a nonsmoker is a good idea. I'm inclined to believe the first is true, but I'd hesitate to use research that proves the first to prove the second (as exemplified by the study I took a look at).

Anyway, if you're in the US and you want to buy e-cigarette products it may be best to do it soon before they're regulated out of existence.