First off, even with the new features and buttons, the Canon 5DmkIV is familiar enough to use straight out of the box. Got things set up, and then read some (not all) of the manual.
4 images, BIRDS ON A STICK! lens correction done, cropped down to main subject for close viewing, no other editing.
1: Handles higher ISOs wonderfully. I shot these photos at ISO 800, one in direct sunlight, one in partial shading and two in full shade. I didn’t run any noise reduction, either in camera or in post. No noise worth mentioning at all.
The Good part II.
2: Sensor is MAD with details! Even in shots #2 and 3 which are in shadow, the fine details in the feathers and on the twigs is clearly visible. Dynamic range is much better than its predecessor.
The good thing this is good because the other is just ok.
3: The high speed continuous shutter speed is a helluva lot quieter in the 5D4 compared to the 5D3 or the 7D2, and faster than the 5D3. This is a good thing, because the low speed silent continuous is slow. And I mean s..l..o..w. That being typed, with the high speed continuous nowhere near as noisy as in previous or different Canon models, it can be used if you need a faster frame rate, but still want to remain rather quiet.
Now, I have only had it for a few hours, reading the manual, setting it up and will have a more detailed review after some serious use.