Any good ones? I researched a year or so ago and all the brands seemed a little bit..sketchy.
/r/electronic_cigarettes has a pretty good FAQ on these types of things, ignore their ridiculous $200 setups though, a bit overkill IMO.
(I am a non-smoker; have tried 2mg and 4mg gum, and find 4mg similar in some ways to having a 'bad trip'. (Light-headedness, freaking out, nausea, time-dilation.))
If I was a non-smoker though I would not start a nicotine habit at all. I wish I had never started smoking, it's a very difficult habit to reverse.