Very large playlists stopped being a problem
Imports that fit in memory
Series import became a constant-memory stream rather than something that grew with the size of your playlist. Temporary storage is throttled, image caches are capped, and progress is reported live while it runs instead of leaving you with a spinner.
One library from several sources
Playlists and network shares stopped being two separate worlds: series from both merge into one list, so a show you have in two places is one show.
Playback that does not fight the import
Background enrichment pauses on constrained devices while you are watching. The work still happens; it stops happening at the expense of the thing you actually asked for.
Episodes that resolve
An episode-key bridge reconciled legacy and canonical identifiers, which fixed a class of bugs where the right episode existed but the wrong one played.