REPOST from another submission I just found:
Using company lists as inclusion/exclusion rules on contact lists would be a game-changer. Sometimes we have extensive lists of companies excluded from contact lists, but instead of being able to create a company list (based on an import) and having that be an “associated company is not a member of list X” on a contact list, we have to paste each individual company name as a value in “company name is”.
It would be so helpful to build a contact list where I could say “the contact’s associated company is a part of X company list” and it would take all of the contacts for that specific company.