One of the participants in the lengthy process to design and ratify an new video codec was NTT Docomo, and they're now demonstrating their implementation of the codec at exhibitions around the world.
Here's a video made by Diginfo.tv showing one such demo. Quite obviously, this isn't the best way to show the ultimate quality of the codec, and we don't know anything about the methodology with which the clip being demonstrated was made.
Same bitrate, better quality
The claim in the video is that for the same bitrate, you get much better quality, and you certainly can see a difference here.
Incidentally, in case you're wondering how there can be different implementations of a "Standardised" codec, the answer is that the "Standard" agrees an overall process. There will aways be many different ways of implementing or coding that process. At a low-level, this is inevitable, and it is at a low level that there is the most room for optimisation; so it is quite possible that different implementations will have differing characteristic.
Download the details
If you ever have a sleepless night, you can download NTT Docomo's account of their participation in the HEVC process here. It does contain some fascinating stuff about how the codec works, but it is inevitably pretty technical. (Note - this link is to a PDF download).
Here's the video, but remember, as one YouTube commenter put it: " You're watching a H265/4K video filmed by a 1080p camera and recompressed on youtube with H264..."