I have been using KK2.0 since I built my first Quadcopter. I am very happy with this affordable flight controller and here is my reivew.
The KK2.0 was engineered from the ground up to bring multi-rotor flight to everyone, not just the experts. That LCD screen makes things amazingly easy to work on and change items on the fly.
Self leveling will need some tweaking, but it can be very stable when tuned. The reason why I am not using KK but Multiwii is I got bored with just flying around after a while and looking for more challenges. Among all the flight controllers, if you don’t care about GPS, telemetry or automated missions, I would go for KK2.0.
KK2 can provide very stable flights, with the camera gimbal support, and at a price so much cheaper than other FC. Even if you don’t like it or have other FC, it wasn’t a real loss. (can be a good backup FC)
I love my KK board save for a few things. I can fly many different multicopter configurations with it.
However it sometimes has gyro drift, I have to put so much stick trim on it mid flight and still have to ride the sticks to keep it level. Also unfortunately, the KK2 does not have a magnetometer to know the orientation and when using auto-level, the ACC must be trimmed first. If the props are not perfectly level or are not exactly the same in the air they move (pitch) which none are, then it will have yaw movement that must be corrected with stick trim.
Final thing, this flight controller is constantly out of stock on Hobby King, probably because there are opportunists buys large quantity from HK and sell them on ebay for large profit. They consider it’s a great joke to rip off anyone silly enough to buy them. I would strongly recommend not to buy from ebay at all, since The KK2 is exclusive to HK so anyone selling them got them from HK in the first place.