Doctors voices: Is vaping dangerous or very useful to help smokers quit and much safer?

Linda Girgis MD wrote a very critical review of e-cigarettes on September 26 in the Physician's Weekly. She concludes: "While it is clear from these studies that much more research needs to be done, there is enough science to be concerned that ecigarettes are not safe like many claim. In fact, they appear to have many hazards that are still being discovered. Are they safer than cigarettes? That remains to be determined. No one can make that claim without more large-scale clinical trials. Until that time, hedge your bets where you will." 
On the opposite side I listened to Dr John Ascroft, who practices in Central England where in 2014 he opened a vaping shop: Dr.Smokeless Electronic Cigarettes! He is interviewed more recently in Peter Taylor's documentary (look on YouTube at 15.33 minutes for this segment). After saying e-cigs are the greatest invention seen in modern times, he concludes they are safe. Whom to believe?