I've done only a little testing so far. The lens mounts on the x5s with some difficulty, have to turn it with moderate force, which is weird because it mounts on my Olympus camera normally. Like the 7.5 mm, it is manual focus. The aperture is controlled by the app, which also recognizes the lens correctly. It balances well with the provided lens shade. If you add a filter, it will need some counterbalancing weight on the rear of the camera.
I've made one test flight including a video and some stills. The video is tack sharp, with no distortion or vignetting. Can't say the same for the stills (shutter speed was set at 1/1000 and 1/2000), but I'm a retired professional photographer and have a high standard for any lens that I own.
Not yet finished with testing, may add more comments later.