I caught the 07:30 flight to SFO last Thursday. Pre-check still funneled you into a merged line but did not have to remove liquids or laptops, and the lines were almost non-existent at that early hour. I've never flown that early out of JFK so don't know if the short line was due mostly to the early hour, or because they've lost tenants in that terminal but it was the smoothest experience I've ever had in T7!