Just purchased the extension, it automatically installed through Creative Cloud, and works flawlessly in my quick testing. Using an up-to-date X-T1 paired to a 10.10.4 MacBook Air. This is pretty much the last thing I was able to do with my Canon system, that the FUJI couldn't. Outstanding.
Canon users be sure to note - images will NOT be saved on both the camera and the computer. Only on the computer, so handle the images accordingly.
I once had a renter in our studio shoot tethered with a Nikon (which also doesn't save to camera when tethering) to a computer guest account - and thinking they had the images on their camera card, logged out (and wiped) the guest account after shooting. Images lost. Ugh.