On one of my Macs I discovered problems with the mini-player. When I collapsed the main window down to the mini-player, the track back icon was focused and thus metadata (song title and artist) would never display. Just the transport controls and the album art. Annoying.
To fix this situation, click on the mini-player and tab until you focus the Up Next menu icon. Then click off of the player. You have metadata back!
I submitted a bug on this and within a day it was quickly closed as a duplicate by Apple – Mossberg suggests a small update is being worked on to bring back duplicate track detection to iTunes, and I imagine this hotfix will come as well.
Keep an eye out. Use the above fix until it’s patched.