The camera has a 42MP BSI-CMOS sensor. Both in good light and low light, whether you're shooting in RAW or JPEG, the images have excellent detail. You can check out detailed studio tests over at DPReview.
Good colors, lots of detail and little noise up to 6400 ISO (though Fujifilm's 6400 ISO is closer to 4000 ISO in other cameras). The camera adjusts the white balance pretty accurately in all kinds of conditions.
The camera will automatically adjust exposure. ISO and shutter speed is ignored. And so is exposure compensation past +/-2 EV. There's also no way to adjust aperture during recording, it has to be set before you start shooting.
With some lenses the tracking is fast and the hit-rate is high while others give highly inconsistent results. Additionally, while overall the faster the lens the better the results, there are exceptions. And while such behaviour is expected with all cameras, the degree to which X-Pro 2 is affected...