Smart thread.
My DH was a 25 year smoker and quit cold turkey 1 1/2 years ago using the e-cig and hasn't lit one up since.
He gets his stuff from the manufacturer and also uses glycerin to gradually lower the nicotine in the oils.
The only negative I have noticed except for some oils that really bother my sensitive olfactory system is, the windshield inside his car.
I have a horrible time cutting the gunk that settles on the glass, vinegar doesn't do it, alcohol does a much better job but it takes mucho elbow grease
which really bothers my hands and wrists.
I try not to complain 'cause I am so proud of his accomplishment.