@xixi_gelly - I have the Oly E-M5, the Panasonic GH3, GH4, and GM1, as well as the original Fuji X100 with fully updated firmware. I also have a Canon 30D and 5D Mark II.
The E-M5 is very close to the AF speed of the Canon 30D. It's not as fast as the 5D II, although it is close enough to make very little difference. The E-M5 can focus in situations that the Canons find difficult, like very low light places with lowish contrast. I can never get the 30D or 5D II to focus properly in a very dark street, for example. The mirrorless cameras boost their sensitivity to make the scene brighter internally, and focus from that image.
If you are dissatisfied with the focus speed of the X100S, I have read that the X100T is faster. At the same time, I am more than satisfied with the E-M5 and other m43 cameras for most street shooting. Some of the Oly primes, like the 12/2 and 17/1.8, have a very well implemented manual focus ring, which allows you to zone focus easily, too.