I just upgraded to Adobe Lightroom 6 this evening, and here are my very preliminary impressions. I've been looking forward to LR6 for its rumoured facial recognition features.
I subscribed to Adobe Creative Cloud (Photography) a few days ago in anticipation of the LR6 release. Once I found out that it was out, it was a simple matter of going to the Creative Cloud app in the notification area, selecting Apps, and clicking "Install" by Lightroom CC (2015).
The download took about 10 minutes, and then it installed Lightroom 6. As in previous versions it does not replace the older version of Lightroom - it installs another copy of Lightroom. Here's my Control Panel.
When it first ran, it asked me to upgrade my catalog. The Lightroom catalog is where all of the edits, tags, star ratings, and so forth are stored. Since Lightroom doesn't actually change your image files, all of the editing you do is stored in the catalog. It's the heart of the system, and of course it needs to upgrade it when you do any upgrades to Lightroom. Since I had a good backup, I agreed and in a minute or two I was in Lightroom 6.
The interface looks exactly the same to me in Library mode... except for one subtle icon at the bottom.
I didn't notice that at first. I poked around a bit and found a photo with a person in it. There's a new little icon at the bottom that you can use to tag a face.
Click on it. Lightroom will try to put boxes around faces in the photo. If it doesn't identify one, you can drag a rectangle around the face. Lightroom will make a guess as to who it is, or if you're just starting out, it'll be blank.
You can confirm it by clicking on the checkmark when you hover over it.
Of course, the easier way is to click that little photo icon I mentioned earlier.
When I clicked that, I was presented with a "Welcome to People View" dialog and a choice between two options: "Start Finding Faces in Entire Catalog" and "Only Find Faces As-Needed". Telling it to start right away will slow down your computer, but I said, what the heck, let's go.
As it churned away, it presented a list of people and its best guesses as to who they are.
You can see that it puts a name and question mark beside those it has tentatively identified. If you hover over the name a checkmark appears and you can click that to confirm Lightroom's guess.
Eventually you will run out of guesses and end up with just unknown people.
TIP: You can shift-select a number of photos and just enter a name once.
Occasionally Lightroom will mis-identify what it thinks is a face. You can remove that.
I'm still learning... there's lots left to explore.
By the way, Adobe has a nice video about face recognition in Lightroom 6.