I'd been smoking cigarettes for 11 years and just switched to vaping 2 months ago. My lungs feel much, much better. I can walk up multiple flights of stairs/longer distances without getting winded. My mouth also no longer has that eternal burnt paper taste, especially when I wake up in the mornings.
So for the purposes of what I switched to vaping for - to ease back on destroying my lungs - vaping/e-cigs work. I used to smoke 2 packs in about a week and a half. I'd say the amount I vape now is the equivalent of 1 pack every month (I don't constantly hit it throughout the day).
I have no doubt that inhaling vapor with that density is still not good, but it's better than what I was doing previously.
As for helping to quit the habit entirely, I think that's the opposite of their goal. All these fruity flavors they keep coming out with seem like they're designed to be popped like candy.