Disappointed to see the response: "Transfer delay between Agent and Caller issue (please open a support case via Office 365 admin center)"
We've had multiple tickets with no resolution -- and this is very well described on tons of https://www.skypefeedback.com/forums/299913-generally-available/suggestions/8563270-remove-the-response-group-answer-delay and http://windowspbx.blogspot.com/2017/02/office-365-cloud-pbx-call-queue-answer.html.
Incoming calls to Call Queues have a 4-5 second media establishment delay (with silence on the both ends of the call), which is infuriating to our users.
(We hackishly work around this using Team Call Groups (e.g. http://windowspbx.blogspot.com/2012/05/microsoft-lync-simple-ring-group-for.html); but means we can't use Call Queues and is very disappointing.)