Seems to be fine in video but with stills I have to hit the AF button.
Edit: I hadn't really read up on this beforehand and it wasn't a reason for buying the camera anyway so not a big deal. Had some more time with it and LV focus is so quick now compared to previous bodies, night and day, tracks nicely as well. Also shot some 1080p video last night at my little owl site so that may be something I use more. ISO seems slightly better than 1DX (DPP's noise defaults are in the same ballpark as my own settings for the 1DX) and the ability to pull up underexposed files is very noticeably better.