I was asked to open my bag once, so they could check my K100 was an e-cig, which they thought it was without my telling them. I understood that; it's a rather odd shape. No other problems, and that includes once to the States and once to Panama, where e-cigs are banned from sale and import for sale, via the Netherlands.
e-liquid in your carry-on must be in the 1 litre baggy with your other liquids and gells.
Lithium batteries not in devices must be in carry-on and must be in either retail packaging or packaging that offers the same protection against short-circuiting. That's an international airlines regulation, not just a rule of thumb or a local thing.