Regarding flavorings - I recently ran out of flavorings (actually, I have one flavoring and I'm bored of it) so I mixed up a batch of unflavored just to try it out.
Turns out I really like it.
It is not entirely flavorless, it has a sweetish taste and the nicotine itself has a flavor.
Since I like it so much and have been vaping it for over a month without getting bored of it, I think I can say that this is probably going to be my all day vape.
Now, I'm not saying that the idea of the potential dangers of flavorings (ie unknown chemicals) worries me whatsoever, but it seems reasonable that unflavored juice is theoretically safer, as it is even fewer chemicals than flavored juice.
Having said that, if I didn't happen to like unflavored juice, I wouldn't hesitate to vape flavored juice.
I guess vaping 3ml of unflavored 10mg liquid per day makes me a tootle puffer, but it keeps me of the stinkies just fine