Track lengths now show everywhere they were missing: playlist and album rows read the length from the column YouTube actually puts it in, and anything over an hour renders as h:mm:ss instead of a three-digit minute count.
Collaborations link properly. Every artist on a track or an album gets its own link, so clicking Metro Boomin on a Future & Metro Boomin record opens Metro Boomin.
Playlists load themselves as you scroll. The Load more button is gone, and pressing Play on a long playlist queues the whole thing instead of the first 100 tracks. Short playlists no longer sprout songs they do not contain: an owned playlist's suggestions section carries its own paging token, and it was being read as more tracks.
Library tabs have icons.