I'm running the Photos app on several Macs and have iCloud Photo Library enabled. One of the Macs downloads the originals as well, the others use the Optimize Mac Storage feature. But I can't seem to find out how to sync faces across the devices.
In Apple Support article #HT204486 it states the following:
Photos lets you tag people's faces in your pictures so you can find friends easily. When you use iCloud Photo Library, these faces automatically update on all your devices.
iCloud doesn't automatically update changes to the names associated with Faces or the contents of the Faces photo album in the Photos app. You can tag people's faces with names on multiple Macs, but the face tags and Faces photo albums will remain unique to each computer.
Now I've read this a couple of times but I really can't figure out what this actually means; the first paragraph says "sure, it can be automatically updated on all your devices" but the second paragraph states "but it doesn't update changes".
Simply put: is it, or is it not, possible to have the same faces on all my macs? And if so, what is the best approach for periodically assigning photos to faces/people?
Note that I've seen a similar (one-liner) question, with an appropriate response. But these do not reflect what is stated in the support article.
Update 27 Sep, 2016: now with macOS Sierra and the accompanied Photos app this is still not possible. Meaning the new "People" feature is device specific and is not synched into the cloud. And is therefor useless if you have multiple devices. There is another question for this as well.
Update 20 May, 2017: with Photos v2.0 (3150.4.120), on macOS 10.12.5, the "Faces" feature has been renamed "People". However, it is still not possible to sync people across macs AND iOS devices.