Regarding the smell/detection at clubs or concerts I've found that it depends mostly on the type of material being vaped. If I have some pungent material, heads tend to turn fairly quickly. So what I've come to do is to use it in the bathroom. I know that's not as heady as sharing a sesh with your friends and not missing any tunes, but in stricter venues I think this is the way to go. Several times people in the bathroom have wondered where the dead skunk is, but they never know for sure because there's no smoke trail to follow.