No, the X100S does not have a speedy AF system. It's really great at some things, but that's not one of them. That said, anyone else with an X100S want to chime in on this?
I've got an X-E1, a two year old and a four year old (and another one due in six weeks). The X-E1 has slightly worse AF capabilities than the x100s, but I have no hesitation bringing it instead of a DSLR on family trips (in fact, it has essentially replaced my other cameras for everything except sports and wildlife). Sure, my Canon's will get AF faster nearly all of the time, whereas the X-E1 is slower (and I've got a 60mm lens that is v-e-r-y slow), but the X-E1's AF speed is still more than adequate. The x100s is said to be better. The X-t1 is significantly better (especially if you are using focus tracking).