I've never used these 'vaping' things, as I gave up smoking (small cigars) years ago.
However, as I understand it, these 'vaping' things provide the nicotine 'hit' without the tar, which is the most dangerous stuff.
All well and good... except for one thing: the nicotine is the addictive component and so 'vaping' will not remove any tobacco cravings from the user.
More to the point, perhaps, is the effect of 'vaping' in public. The participants claim that it's harmless, but surely 'second-hand nicotine' is likely to encourage addiction amongst anyone who is nearby, isn't it?