Yeah, I should report it myself as well. Weirdly it worked fine on my iPad, so don't know if it's just a random upgrade issue.
As far as I've tried it, the facial recognition seems to be quite good. It's mostly got all of them right, it's struggled differentiating a few but they've been very close relatives and look quite similar. There are a number of instances of separate files for the same face but most of them are due to either weird angles, difficult lighting, other objects obscuring the face or other issues with the photo itself. It's definitely a lot better than it was in El Cap, whether it's better than Googles AI I'm not sure. I tried Googles photos service for a bit but I didn't give it a very large set to work on, it still made mistakes even so. Although that was with the object recognition as Face recog on Google photos isn't enabled in the EU at the moment.
The more we train it, the better it should become. The only downside for me at the moment is that the data isn't shared over iCloud, so each device has to be taught on its own. At least for now.
Edit: After I give the separate file the same name as an existing face it offers to merge them. Then detects other faces that are the same, it got all of those right.