It might have millions of users registered (or users however they count them) but I see it slowly becoming irrelevant compared to what it used to be, at least.
-Zynga is removing ton of games from facebook and getting lay-offs. Zynga, the king of FB games? I mean sure, most of the games werent great but it had millions of users. I guess at least FB gaming is becoming irrelevant (thank godness)
-They are adding tons of new, and odd, ways to get money from even regular users. Pay us to promote your post - otherwise it will be hidden from 80% of page followers.
-They are even planning on adding 0.99 dollar fee for the luxury to send message directly to someones, who isnt your friend, inbox.. not their "other box" (Its currently 100 dollars "to reduce spam on test phase")
And many more other things relating to stuff like this and others
As for personal experiences
Twitter was never "the thing" over here. So I didnt see point to it. But once I started using it, it felt much better. Got more replies than in FB, send more messages than FB and just generally followed more people (not compared to pages yet)
When I go to FB's frontpage it just screams of apathy from actual users. Hardly anyone posts statuses anymore. And I hardly see comments or likes on them that much.
Pages use their twitter feed's or other social media feeds more actively than FB.
Only things I see is page spam and adverts, this is where it have become then huh?
I dont see anyone leaving it yet (where would they go, google+? haha) and since FB is easy to understand for older folks. Maybe people will stop using it but leave their profile there like on myspace and move on once theres proper site to move into.