I attended Wells Fargo Securities’ “2nd Annual E-Cig Conference” last week, and if I had to describe the mood of the speakers it would be a cross between cautious optimism and deep frustration.

“E-cigs,” of course, is shorthand for electronic cigarettes. Executives from the still-new industry happily talked about its rapid growth and their expectation that it would continue. Bonnie Herzog, who follows the industry for Wells Fargo, reiterated her belief that in 10 years, e-cigarette users will outnumber smokers.

“The winning product hasn’t been invented yet,” said Craig Weiss, the chief executive of NJOY, an e-cigarette start-up. What he meant was that while the e-cigarette devices developed so far have helped some people switch from smoking to “vaping,” they haven’t yet become so good as to “obsolete the cigarette,” which is, he says, his company’s goal. But that day will come, he is convinced; the industry is innovating like crazy.

Yet, at the same time, most everyone at the conference expressed dismay that e-cigarettes aren’t being embraced by the tobacco-control community — even though they are much less harmful than combustible cigarettes, which kill 480,000 Americans each year. Are e-cigarettes completely safe? asked Saul Shiffman, an addiction expert at the University of Pittsburgh. “There is not enough data to say that,” he acknowledged. But on a relative basis, electronic cigarettes are far preferable to the old-fashioned kind. After all, e-cigarettes are essentially nicotine delivery devices, and while nicotine is addictive, it is the tobacco in cigarettes that kills.