Ever tried to change the status of mulitple records or delete a bunch of pages?
In v3, this could take a long time: click "delete record", confirm the deletion, wait for the page to reload. Repeat those steps for all records.
In contrast, v4 finally introduces batch-actions. Every module may register additional batch actions in order to process a list of records, the progress is shown using a funky dialog.
To proove it: Screenshot!