when importing new tracks it would be helpful if the songs that dont have overviews biult are high lighted a different color

If you click on the overviewbuilder it will automatically build overviews only on the new tracks.

Also you can always sort your tracks by the added/import date. That helps you to identify the new added tracks.

It would really be nice if the tracks that have overviews retained all fields if you rebuild your recordcase (i.e. - length, bit rate). About once a year I re-organize and build a new recordcase; only to end up rebuilding overviews.