I've been looking into the kayfun, but I haven't decided how I feel about it, yet.
I only use Kayfuns now. I used to own a Z-Atty-Pro from Provape/ZEN. Got sick of the waaaay to open airflow that was not adjustable. I ordered two Kayfuns initially, then ordered 2 more after I was blown away by the performance of the device on top of a Provari.
The kayfun (I wouldn't buy a clone) is as no-brainer as buying the Provari was. As long as you are OK with rebuilding the coil/wicks, then you WILL save a ton of money over a cheaper atomizer such as a Kanger with replaceable heads. Those heads are comparatively expensive against the kayfun. You either pay more for the device up front, and save tons over time, or you spend a ton of money on replaceable heads. The cost of 100ft of 28 gauge Kanthal wire and organic cotton balls from Walgreens or CVS (drug stores) is nothing compared to the cost of replaceable atomizer heads. I compare their business model to that of all printers. They sell you the printer cheap, and empty your wallet with replacement ink cartridges. Kanger's business model is the same as all printers. Sell you the device for nothing, and empty your wallet with the replaceable heads.
Buy a Kayfun. You won't regret it.