Nicotine constricts blood vessels. Yep.
The real question is what are the health effects of long term nicotine use. We don't know. There's a lot of long term data on smoking tobacco products, but none really on nicotine by itself. That's that.
Then, there's two messages out there that get me a little angry:
1. Nicotine is bad for you because one drop of 100% nicotine on you skin will kill you. This is utter nonsense, the effects of a substance vary greatly with dose and rate of administration.
2. Nicotine constricts blood vessels in the nose when placed on the mucosa (fact), nicotine raises blood pressure a little for a short time when taken in the amounts found in a cigarette (fact); smoking tobacco is linked with increased risk of high blood pressure and cardiovascular problems (fact). Therefore, nicotine is bad for you (non-fact). This is a bait&switch kind of thing - there's no proven link between the effect of nicotine on short term and the long term effect of the tobacco, whereas other dozens of substances in the smoke are clearly linked.
The FDA is doing its work as if their hypothesis that nicotine is bad has been proven. Nicotine is really bad because it helps getting you hooked to burning tobacco, but it's not clear that it is otherwise.
But, then, they say - maybe we should ban it until it's proven safe. Well, it doesn't work that way - no new product is held to such high standard. Every day, hundreds of products that may be dangerous, including FDA approved medications, hit the shelves and are given the benefit of the doubt until there is some evidence that they are harmful.
On the other hand, my newest pet peeve is that products such as these and these which will definitely kill you, are not treated with sufficient skepticism and in fact are subsidized by the federal government.