It does the same as the @ operator, except that it takes care to prevent a very bad bug that existed before PHP 7. Details at https://phabricator.wikimedia.org/T253461

If there are other issues or benefits, please write them on the task. The overhead of AtEase is prerty minor, so really any benefit at all is likely to tip the balance toward keeping it. But, in the event that there isn't any, then perhaps we should slowly phase it out.

Best, -- Timo