I personally do not have one. I will hit my friends' e-cig every one in a blue moon. I have no interest in getting one myself. I feel like they are not a great way to stop smoking because you are still bringing a foreign chemical into your body. They aren't as bad as cigarettes, but the healthiest alternative is to let your lungs be. This is an article posted by /u/bradd that basically says we don't know enough about long term health from e-cigs to make a call. There have been a lot of studies, but many of them have been supported by an interested case, leading to heavy bias. It does say that they are helping people to quit smoking, though.

As a follow on comment with ecigs you never really break the habit of smoking. You just switch it out with a somewhat less hazardous alternative. I think they can work great to break people away from cigarettes, but they are not a long term solution. If you keep that habit their of puffing up every time you have a craving it is a whole lot easier to fall off of the wagon.