Been playing with my ps4 for the last 6 hours or so! I only have BF4, and the servers were GODAWFUL until about 2am.
So, it's pretty much exactly what I expected. It certainly looks better, that's for sure. I notice it most in particulate effects, bits of buildings exploding, etc. Plus, I imagine that Dice probably didn't change much between the ps3/ps4 versions. That being said, it is probably the least noticeable difference between console generations.
I downloaded the two free games for PS+, but haven't had a chance to play those yet.