Picked up an iStick Power Nano kit from the VT store a week or so ago for my wife, as she thinks even the iStick 40 is too big for her hands. The Nano is about as big around, and about 75% as tall. Only the top 1/3 of the tank and drip tip make it taller than the bare iStick 40, it's pretty compact.
I filled it with my favorite 70vg/30pg juice (gotta try it before I turn it over to the missus), and used the factory installed .75 ohm coil. I started out at 10 watts and over several tanks settled in at 14 watts. Good flavor and a decent cloud, but not enough to obscure the TV while chain vaping it. No dry hits, the juice holes in the coil are quite large. The airflow is in my opinion a bit on the restrictive side for DL even wide open, but it is possible. Think somewhere between the full open and mid setting of the subtank mini.
I haven't messed with any of the different settings, just used it in watt mode. The battery lasts through 3 tanks give or take with the .75 ohm coil at 14 watts. I haven't tried the .3 ohm coil that comes in the package sealed in it's own blister pack, and probably won't for a while, the missus has discovered the Nano and refuses to give it back.
Overall it's a good little unit. In wattage mode it just plain works and so far has no little quirks. Also as far as I can see it works exactly like the full size 80 watt iPower.