Writing for the B&H Photo Explora blog, Justin Dise took the Sony α7R II for a 4 Day 4K test drive.

"Ever since it was first announced, the α7R II is a camera that I couldn't wait to get my hands on, as it is the first in the a7 family to record 4K (UHD) video internally; a feature that many α7S owners—myself included—would love to have. The camera seemed almost too good to be true, offering internal 4K (3840 x 2160) recording in full-frame and Super 35 modes, S-Log2 gamma, 5-axis in-camera stabilization, and the promise of good low-light performance despite its 42MP sensor." -Justin Dise

Check out the full Exlpora post. Also, at the time of his writeup, Dise didn't have the latest firmware update installed on his α7R II. You can find that update here. 

Here's a list of improvements of firmware version 3.00 over the previous versions:

Improves 4K movie recording time when using the vertical grip (VG-C2EM) or when the APS-C/Super35mm mode is activated.
Improves picture quality.

Benefits provided by previous updates and included in version 3.00:

Adds the selectable feature for uncompressed 14-Bit RAW image capture.
Adds support to output video via HDMI during use of the Remote Camera Control software (still mode only).
Reduces the chance of the camera changing to front focus when shooting certain scenes. Note: This symptom rarely occurs.
Decreases chroma noise when Long Exposure NR (Noise Reduction) is set to Off.
Note: The noise does not occur when Long Exposure NR is set to On.
Improves continuous shooting at Hi speed so that it can be used just as long when using the flash as without the flash.