I just remembered, while working with custom entities, that Drupal 8 was supposed to bring UUID support and replace the old "entity id" keys but then I've also noticed that the old fashioned entity id key is required by tye EntityType annotation and interestingly the UUID key is just optional.
Is this so that urls/entites are easier to remember by their "nid"?
And most importantly: should we use UUIDs or entity ids in logic and/or database operations?
Is this the final approach or we'll see entity id disappear in beta/rc/stable release?
Personally I don't see any good reason to keep using the typical serial keys when we have UUIDs now.