Upon running some tests -- Searching the Library unfortunately, is not as accurate as Filtering for specific Content Tags, which is absolutely correct... 100% of the time.
I'll be depending on Tag Filtering more and more... however:
Going "Back" through existing libraries it would be great to select multiple videos and batch apply tag(s).
Right now every video needs to be "opened" to assign Tag(s).
Going "Forward" it would be great to assign Tags in the Upload Files so sets of videos uploaded would absolutely have the correct tags immediately.
Since Uploads of single or multiple files can be stacked, individual files wouldn't need to be assigned tags -- sets would be more than adequate.