I got mine today as well, it's working GREAT so far, I'm very impressed! Especially with the price.
The tank seems to be Smoktech's regular eGo diameter DCT. I guess most people would know that by the pictures.
Anyway, performance is great, even with the stock coil surprisingly. The one that came on mine is 2.3ohm. It's a pretty easy to use piece, I have no experience with the real Killer so I have nothing to compare it to, but I'm happy so far.
All I did was unscrew the thing, prime the coil and wick with a bit of juice, screwed it back together, put it in the tank, filled the tank, and then starting vaping. You unscrew the unit while it's inside the tank to increase juice flow, and unscrew it to decrease juice flow.
The only problem I have, is figuring out an easy way to fill the tank! You cannot slide this out of the tank like you would with a normal carto, so you can't fill it that way. The only way I found to fill it was to remove the top endcap, fill it, and then push the endcap back on. Doing so creates overpressure in the tank and forces some juice into the atty flooding it. But after blowing it out it doesn't seem to flood or run dry, it's just working great.
Anyone know of a better way to fill it? I'm thinking of using it in my AGR, that way I could use the phil hole (

) instead of removing the endcap. Plus, since the AGR locks the base of the atty into the tank, it would be easier to adjust airflow I would imagine by spinning the top of the atty.
I too want to buy more, I feel this thing will be a big seller. I wasn't too surprised to see madvapes sold out already, hopefully they will get more in stock. I wish they would sell JUST the atty itself, I don't want to have even more cheapy tanks sitting around that don't get used.
Overall worth way more than I paid for it, other than the difficulty filling the tank I have zero issues with this (for now)