Facebook rolled out an updated interface and a bunch of new features yesterday, and I spent some time yesterday evening looking at what they had did. There is much buzz about a new music-sharing service, but to me, the most significant change is the addition of "lists," which is the equivalent of Google+ "circles." The concept is identical: you can group your friends and contacts into sets, and you can look at only what is going on in that set of contacts, rather than having to plow through every item that gets posted to your wall.
If you have lots of friends, this is a major improvement in usability. And it probably would not have happened if Google+ had not built a better mousetrap. Facebook was forced to respond, and they did. I have seen some grousing about how long it took Facebook to add the new feature, but as an old applications programmer, I'm impressed that Facebook rolled it out in just about three months, to 750 million users. That's good software and version control management.
Facebook has also changed the way you set your privacy options, and to me, it is also a big improvement--it's much easier to understand now who can see what.