Cigarettes kill 50% of long term users. Being safer than that is not a big accomplishment.

I agree completely. I don't mean to suggests that vaping is a good idea, only that it apparently doesn't have PICs in it.

Being safer in general isn't. Being safer while also being a psychologically acceptable substitute for smokers - this is the achievement.

This is correct. The mixture is almost always propylene glycol, vegetable glycerin, nicotine, and flavoring. I don't know of any negative effects of propylene glycol and vegetable glycerin, and as long as you don't use a carcinogenic flavoring (they exist) your biggest problem will likely be nicotine.

I don't think nicotine is good for you, but vaporized nicotine seems much less dangerous than smoking a cigarette.

Even glycol and glycerin vapor are probably not a good idea to inhale. They could hardly be as bad as smoking cigarettes, but so far basically anything you breathe in that isn't air turns out to be a bad idea once we study it thoroughly.