Awareness and use of electronic cigarettes (e-cigarettes) is increasing. Questions regarding positive (e.g., smoking reduction/cessation) and negative (e.g., delay of cessation) potential public health consequences of e-cigarettes may be informed by studying dual users of e-cigarettes and tobacco cigarettes. A cross-sectional online survey assessed demographics, product use patterns, and beliefs about relative product benefits and harms among dual users (n = 350) in the United States using the website Amazon Mechanical Turk. Compared to tobacco cigarettes, e-cigarettes were used less often and were associated with lower dependence. Participants reported a 30% reduction in self-reported tobacco cigarette smoking since beginning to use e-cigarettes. Reported primary reasons for e-cigarette use were harm reduction and smoking cessation. E-cigarette use was reported as more likely in settings with smoking restrictions and when others’ health could be adversely affected. Conversely, participants reported having used tobacco cigarettes more often than e-cigarettes in hedonic situations (e.g., after eating, drinking coffee or alcohol, or having sex), outdoors, or when stressed. Participants were twice as likely to report wanting to quit tobacco cigarettes compared to e-cigarettes in the next year and intended to quit tobacco cigarettes sooner. Tobacco cigarettes were described as more harmful and addictive, but also as more enjoyable than e-cigarettes. Participants provided evidence consistent with both positive and negative public health consequences of e-cigarettes, highlighting the need for experimental research, including laboratory studies and clinical trials. Policies should consider potential public health benefits of e-cigarettes, in addition to potential harms.