I used to work with a kid who had just started messing with electronic cigarettes.  Now, certainly, he hadn't been smoking two packs a day for twenty years, so keep that in mind.  When I asked him about it and started ribbing him a little for having just taken a step up from the candy cigarettes we used to play with- you remember that were actually gum with powdered sugar you could blow out the end like smoke- and he told me he hadn't smoked a real cigarette in almost three weeks.  Again, not the 40 year old with a life-time of addiction to break, but still significant.  Apparently there is some form of nicotene or other in the mist that users inhale.  Not as much as a cigarette, but enough to take the edge off the craving, and then there's the familiar act of smoking that probably feels comforting and reassuring, unlike chewing gum or applying a band-aid-like patch.  I guess it makes sense that technology should answer this problem for our smoking youth.