Yes I have a couple although I do keep breaking the damn housings in crashes! Very good little camera with excellent quality. Not quite as good as the expensive GoPro black but I find the 4k on the black doesn't work very well anyhow perhaps due to the camera needing to deal with vibrations etc so its not something I ever use.
Battery life is about half a day at the track and I charge it over lunch. The big benefit is the single touch to turn on and start filming and quick and easy battery management. You just plug into USB and it's charged in an hour or so.
They dont have the GPS data that the bigger Gopro Black cameras do but thats not as useful as it sounds since you cannot do much with it other than add dials to your film. That said Race Technology look to have released analysis software that looks really interesting. I'm going to trial it at Alcarras in a few weeks if I remember!