I've made a little test to check your impressions:
Leica S2 with FW 1.3.0.0 + 120mm CS lens, on tripod.
Lens focus manually turned to min focus distance then start autofocus on my kind's bike 5m away.
Several tests gives an average 4,6sec for acquiring focus.
Same test but with lens focus manually turned to Infinity, average focus acquisition of the 5m distant target: 1,6sec
Then FW update of the S2 to 1.4.0.0 and lens update.
New run of tests, exactly at the same conditions than before updating.
Average acquisition time from min focus distance: 4,1sec (0,5s less) = 11% speed gain.
From infinity to target, it only took an average of 1,1sec (also 0,5s less) to acquire focus = 30% speed gain.
Based on the very nice round up of the new Leica S from David Farkas and his explanation of the new autofocus mechanism, it could be that the S2 also gains in AF speed thanks to avoiding the start-stop-restart of the AF motor, which could explain the same 0,5s gain in speed.
Of course this is just a speculation & 1 test of 1 body & lens on just 1 shooting condition. But this test + some handheld use at poor, rainy light conditions makes me believe the better AF speed after FW update is not just an impression, and that's great.