I've done a lot more experimenting with different set ups now, and I am still really disappointed in the iStick 40w for what I wanted to use it for - driving an ego one mega with .2ohm TC coils. This combination blows. and without temperature control, I've found it REALLY easy to burn these coils using vw. There is just not very much wicking material in there, and they get hot so fast, the coils really need the TC to not burn, unless you're using them at really low wattage, under 17w.
I've been using the istick set at 600º with the ego one with TC coil, and it keeps it from burning, but gives a totally lackluster vape. just disappointing puffs all the time. Reminds me of vaping a kanger emow.
I tried the istick with a subtank with a TC coil. This worked better than it did with the ego one clearomizer with TC coil, I still had to run it at 600º to get a decent puff. And after 3 puffs on that setting I was able to get a very burned cotton hit. Nasty. Turning it down to about 560º avoided the burning but then the puffs were not very rich or flavorful. This combination works, but still was off by a LOT and not as nice a vape quality as the same tank on an IPV4 or M80, set to a much lower temp.
The ego one TC coils would not even fire on the IPV4. So, maybe those coils also suck. I've also noticed if I can somehow get the resistance to lock in at .22 instead of .20 or .19, it almost does what I want at 600º. but even the resistance lock doesn't seem to really function as expected all the time, and unless you never remove the tank to use something else, you can't keep it locked for ever.
I also built a velocity rda with dual clapton coils that come to .58ohms to run on the new iStick. At 40w, it's barely giving me the richness I expect. I ran the same tank at 40w on an IPV4, and it was much nicer, a noticable difference. Ideally though, the velocity with these coils needs around 65w to really shine, so the istick is a fail for this use as well.
I really don't think this istick meets any of it's advertised promises. It barely does temp control, and does not do so in any way that would allow for it to protect you or give you a consistent vape. It does not seem to output 40w of power. And at it's 40w setting, the battery drains insanely fast. So, in essence, I am better off with my 30w, because it's more predictable and lasts longer.