A couple of tips from experience on the Security Checkpoint --
1) Put your liquid and spare carts into your ziplock bag with your toothpaste, etc for the x-ray this way they can visually see it if they think it looks "funny" on the x-ray.
2) Put your e-cig (battery, atty, cart, etc all assembled) directly in the "tub" with your laptop, etc but not on top of anything -- they need to be able to see it clearly on the x-ray.
I once had 7 cartomizers perfectly arranged in an empty, clear prescription bottle and left it in my coat pocket in the x- ray. It looked about like this from the top:
o o o
They were quite puzzled by it (I'm sure it looked quite odd!)
Also, the TSA has said explicitly that e-cigs are fine to take through security: http://blog.tsa.gov/2010/05/e-cigarettes-go-or-no-go.html
As for vaping on the plane -- I usually just chew some nicotine gum, but, if I do vape, I only do it if I'm at the window, the person next to me is sleeping (or clueless), with as much discreetness as possible (exhale into shirt) and ONLY if the window shade is down and the lights above are off. I imagine what I'd think if when looking at the person in front of me I started seeing "smoke" and knew nothing about e-cigs. I bet people would seriously freak out!