It's a bit underexposed, but yeah it's not bad for a smartphone camera (will small optics and a small sensor). By default the Lumia 950 does some post-processing/enhancements to the image. So it's part sensor and optics, part firmware, and part software (just like ALL other digital cameras). The Lumia 950 produces good images not only because of the camera, but also because of everything else the phone has and what they "do" to the image before displaying it on the screen.
I'm not comfortable with devices that considerably alter the original as-in image, but for most users the results of the Lumia 950 will be useable.