As low as 20ms in some beta testing - but still in early stages of course. It's going to take time to iron everything out. I imagine they will have problems to deal with at the point they open it to the masses because of the huge draw on the system.
Bunch of smart people over there at Starlink - they'll figure it out.
Lasers got to have pin point accuracy to link them all together, going to have master satellites to feed back to with a huge ground station uplink????, for the total through put that's going to be needed with millions of potential users.
Sure they've got it all planned, but still, mind bogglingly complicated, way too many things to go wrong.