In my recent experiences processing times have been VERY variable. A week or so ago it took 2 hours to get the documents verified. On the contrary, for my last flight a couple of days ago i submitted everything around 40 hours prior to departure and was cleared on my way to LHR (around 3 hours prior).
It is useful when travelling with hand baggage only as it allows to get a boarding pass on mobile. I wouldn’t even bother with checked baggage, as the documents can be verified at check-in…