Issues with e-cigarettes:
1) they bypass laws regarding cigarette advertising: compare e-cig packaging with cigarette packaging; this is problematic, especially for youth (the non-users most likely to be vulnerable to advertising for such products)
2) contrary to what is portrayed, they are not interested in helping people quit tobacco usage: tobacco companies have a large stake in this business
3) e-cigs minimize the danger of tobacco, by making the "delivery mechanism" seem most problematic, and thus "solvable"
4) there are other methods to deal with cigarette addiction (nicotine addiction, in particular): they just aren't as sexy
As for the law itself, it sets a historic precedent (if it truly bans e-cigs outright, rather than just on city property/public spaces): tobacco products can no longer skirt flat out prohibition.
I find it ridiculous that:
1) Juul's spokesperson cites "thriving black market" creation as a problematic side effect of this law: the point of prohibition is not to stamp out usage entirely (as history has shown this is not feasible), but to make it more difficult than usual to obtain said prohibited product. Its all about probability. Furthermore, when it comes to habits, even small barriers to existing habits can go a long way in changing them (and conversely, removing small barriers to new habits can go a long way in promoting them).
2) Commenters claim that e-cig users can just go to other jurisdictions, making this law "pointless": again, its about introducing barriers.
The law is far from a perfect solution, and I doubt it was intended to be, but it's just a small step in the right direction.
Finally, I think substance abuse problems fundamentally come from a lack of satisfaction/connection with the world around us. There are a billion and one ways to handle this issue, and I think normalizing substance usage only works as a barrier to usage (e.g. Netherlands: remove the "sex factor" due to "prohibition") when the substance has already been commonplace for years. E-cigs are new enough that prohibition can send strong signals to people who might be considering getting into it, especially because as a society we have successfully built quite a lot of "energy" behind the idea that tobacco usage in general is fairly harmful/not sexy (c.f. the situation with alcohol, where it remains synonymous with "socializing").