How long does the new Testflight Beta review process usually take?
Yesterday at 6 pm I uploaded my beta build for review and it's status was waiting for review. This morning the status had changes to "In review" but now, 13h later it's still "In review". I will update this post if my app build had been approved.

EDIT: A day later in the morning it was approved. The total proces from uploading to being reviewed took 1 and a half days.