Is stealth vaping an issue ?
Is the small size the reason the istick is selling ?
Small size is not just for stealth. For most people, smaller is better if no quality is sacrificed, and the iStick packs a pretty hefty 2200 mah. I worry that it would be too small for my personal comfort but I've got very large hands. For people with average mitts it seems to be delightfully compact, capable and powerful.
Stealth vaping? The only times I've attempted to hide my vapor was when I was hanging out in the hospital because my Dad was there, and in the restroom of an Amtrak train. Concealing the fact that I was vaping did not depend on the size of the mod I was using. Others, though, seem, from what I've read, to be more familiar with such situations.
For me, if it isn't producing a visible cloud, it isn't producing enough vapor for me to find worthwhile anyway. So in my opinion, the major appeal of the small size of the iStick is convenience and pocketability, not concealment.