Purely anecdotal - I came through on Tuesday and was worried after my connection time was changed from 2h45m to 2h15m.

We landed at 0550, but couldn't exit the plane until 0600. They were handing out express path passes when your exited the plane for those with 2h connections (I wasn't offered one).

Was slightly delayed at immigration as staff were still turning their computers on - however this was in the "ESTA" line, the US line looked to be moving well.

No wait for baggage and no line at customs.

Dropped off my bag at the connecting flights section and was through security at 0635 at the new tunnel between TBIT and terminal 4. Was able to stay airside all the way to terminal 6 and got there shortly before 7.

Assuming no long lines at immigration and an on time arrival, it should be a breeze to get over to terminal 8 especially with being able to stay airside.