So far I've been testing the Zion with what I assume will be the stock stem (ie the one short enough to be stored inside the device) as I imagine most users will start with this setup. I was using it dry, and unless you reach high temperatures (read above 200°C/400°F) I think it provides adequate cooling.
You can judge with some practice the correct timing to release the trigger button by feeling how hot the vapor hitting your throat becomes. At the end of a session or when going high in the power range, it can start getting quite hot but nowhere like my Firewood 2.1 with stock stem, which is barely usable this way (in fact I always hit my FW with a stem extension using an Ascent straw and a small silicone tubing link)
Yesterday I tried one of the two longer glass stems I got for testing. I assume those will be sold as accessories and I have no idea if the FC10 will get them too (I wish you do, but it would also make sense if RBT make them separate upgrade parts) I can only recommend them anyways as they clearly cool the vapor better and offer more comfort at high temps. Of course if you plan to use water filtration then it doesn't matter much...
Last night session pushed the batteries hard and was bordering the integrated power cutoff mechanism. My cells ended at 3.24V and 3.28V respectively, starting to get noticeably out of balance. They nonetheless started charging with one solid bar out of 3 on my Nitecore charger.
Now that Ashton and me got acquainted, it's time for me to issue my verdict. I don't know if it is because I got some prior experience with a similar manual drive vape (Firewood 2.1) but I felt at home pretty fast with the Zion and found that the technic, while similar overall, felt much more easier in practice. You need to focus on what you are doing if you don't want to get a blank hot air hit, but if you follow your routine then the device will gratify you everytime with ample tasty vapor.
I'm more a slow sipper, partly due to my damaged lungs and partly due to my spliffs smoking background, but I must admit being able to get such large lungfuls clouds with so little effort feels very rewarding and medicates you very fast. It's quite easy for me to overdo the Zion and blow clouds I wouldn't be able to get with my conduction portables. At times it's almost too much for what I'm after, this is why I've been using it exclusively on the evenings so far.
A friend of mine came to my place the other day and tested Ashton briefly. I just gave him short instructions and let him hit it... After exhaling a very large cloud he said "Wow, I got it, this is the equivalent of a bong but with vapor!".
My impressions are overall very positive and I can only recommend this device, it works pretty well.