I always switch IS off for any sort of action photography, so that may play a part in me not having any issues.
Perhaps I wasn't clear enough in my original post, but much experience on my part allows me to confidently state that there isn't a hope in hell of an X-M1/X-E1/X-Pro1 actually properly tracking a fast moving car or plane, CAF working or not, however I find CAF does help significantly, and is still a far more efficient method than using SAF.
My method goes a bit like this (in CAF mode), remember I'm talking mainly about objects that will pretty much fill the frame at 100mph+, not kids moving around indoors or anything.
1. Grab an initial lock-on to the subject by half pressing.
2. Continue to track the subject without touching anything on the camera, the camera will make a vague attempt to track the subject, enough that it's still easily definable through the EVF. This holds up pretty well even tracking subjects over fairly significant distances, or subjects moving towards or away from you.
3. A final half-press and then immediate full press at the point of taking a photo.
I would never expect it to find my subject quickly without initially doing anything at all (i.e. A fast moving jet quarter of a mile away), to be honest that thought never even crossed my mind, it needs pointing in the right direction. Once you've defined the subject it makes a reasonably valiant attempt to cling on to it, certainly good enough that by the time you want to take your shot, it's only slightly out of focus so will lock on properly instantly.
This method was tweaked from how I used to shoot with various Micro 4/3 bodies, ironically it's actually easier with an X body than it ever was with an O-MD/G5 etc, despite the blasting Fuji AF gets.
