I'm not totally sure, or even how accurate the reported concentrations of nicotine is in juice from various manufacturers. For example, I'm on 36mg and 24mg, from Mt. Baker Vapors, but as far as I know, there is no body that checks to verify whether or not this is so.

I haven't been following the research closely, but I do know that there is a lot of interest in the technology. Furthermore, there have been some issues in how certain studies have been conducted, for example, some studies that assume that most users inhale vapor the same way that they would smoke. While this is certainly one way to use e-cigs, I was told that for the best absorption of nicotine, it's recommended to draw the vapor into the mouth, more like how one would smoke a pipe or a cigar.

Another thing that makes research a bit tough, is that there is a lot of variance between devices in terms of how much vapor is released and at what voltage and then again in the actual nicotine juices used and the various flavoring additives. Until good research can be done, I think that many people who are not smokers or users of these devices will continue to be resistant to their presence and will continue to treat them as a nicotine delivery system in the same class as cigarettes, which is lame and unsubstantiated, though a bit understandable.

What bothers me is the stigma against smoking. If that's the dirtiest thing that people can imagine in their everyday lives and worry about it to the point of trying to prevent others from making the choice to smoke, then I do think that's a real problem. Personally I'm more worried about antibiotics and pesticides, not to mention nitrogen pollution or even indoor air quality.