I am a light smoker, about 10 per week. I tried the electronic ciggies, mostly because of my fascination with gadgets. For what it's worth I think they only re-enforce the nicotine habit. There is no substantial "throat hit" with these things, (something only a smoker would understand) so you end up sucking ferociously on them and burning your lips with the hot vapour. I found myself pulling on an e-cig for half the evening where normally I would have only a single cigarette. Mine ended up in the bin.
As for substantial evidence about them being safer than real cigarettes, that would be easy considering how lethal real cigarettes actually are. But bear in mind that these things are not regulated and come from China, two facts that amount to the end user having absolutely no idea what he/she is actually inhaling. They may eventually serve a purpose as a quitting aid but only if they were to be manufactured in a regulated/controlled environment.