In order to get a taste of what the leaf shutter of the Fuji X100s can do, my friend and fellow HauteLook photographer Adam Queen did some modeling for me.
The set up: The Fujifilm X100s, 1 Lumopro LP180 (bare and hand held at arms length camera left) and triggered with Pocketwizard Plus III transceivers.
We were able to sync the LP180 to 1/1000th shutter speed, bringing some detail out in the clouds and making these mid day portraits very dramatic. The 1/1000th shutter speed in this case is limited by the Pocketwizards ability to send the signal. In other tests, I was able to use a hard wire sync cable to sync the flash all the way to the camera max of 1/4000th. This is easily one of the coolest features of the X100s (and other leaf/non focal plane mirrorless cameras).
These were shot in all of about 10 minutes with minimal gear, a testament to what a useful tool this can be for the professional photographer.