In his review of the Sony α9 for Gizmodo, Brent Rose describes using the camera in situations ranging from fast action to long-exposure night shots. His overall evaluation is pretty clear.
Let's put that in context...
"The α9 is equipped with a wide autofocus system that covers more than 90 percent of the frame. It is lightning fast and extremely accurate, even when shooting at its blistering top speeds. I tested it with running dogs and with people on a zip-line flying right at me. Even at a shallow depth-of-field (f/2.8) and while shooting 20 frames per second, the focus was recalibrated between every single shot and it was dead on nearly every time. Nothing else on the market comes close to this kind of performance. It’s bananas."
He goes on, describing not just the impressive specs, but the actual experience of shooting with the camera.
"But let me try to explain what it’s like to shoot with this camera. Not to get hyperbolic here, but it almost feels like you can’t miss. An example: I was walking by a creek with the camera dangling off my neck, powered off. I saw a golden retriever emerge from the water and start to shake itself off. It has already started shaking before I’d hit the power button to turn the camera back on, and yet I was still able to fire off a burst of 14 shots, and in each one every hair on the dog’s nose (and every water droplet flying off of it) was crystal clear. My α7S (which is by no means slow) wouldn’t have even gotten a single shot off in that time. Using the α9 almost feels like cheating."
See the full review at Gizmodo.com