I've traveled with various eGos, Innokin VV V3s, my Firebox squonker, an eVic... no problem. I have had an airport rent-a-cop ask me what the squonker was, mainly because I had forgotten to take out the juice bottle inside, but that's it.
One thing I would NEVER consider flying with is my Innokin Cool Fire 2, for obvious reasons
EDIT: oh yes, I forgot: to bring nic juice in countries where it's not allowed, I transfer it in unmarked bottles and stick fake labels on 'em with "0 mg nicotine" clearly indicated. I've yet to be asked what was in the bottles though, but... better safe than sorry.
EDIT 2: don't bring expensive stuff to/from the US: if your vaping kit attracts a TSA goon (sorry, "agent"), they'll steal it from you (sorry, "confiscate it for safety reasons").