Yeah, i found it seemed to take longer than the Milaana too, but i think that makes sense, since Milaana is 'full on' as soon as you hit the trigger, whereas Zion seems to build heat (and build and build and...). This is offset, though, by being able to hit the trigger early on Zion to let the heat start building without fear of combustion (sometimes before i have even exhaled the previous hit).
With the power knob, rather than thinking of percentage or clock orientation, I found pointing the dial at the stem was around perfect setting for me. I can adjust up or down depending on mood, but found anywhere in this area as ideal and easy to remember.
I also find that the shape of the Zion leads me to use my left hand as the most comfortable way to hold. This is the only Vape i do this for, but surprisingly, I like it. Plus It frees up my dominant hand allowing me to do other things with my right hand while vaping (and that's not an invitation for the out-of-context thread...)