The Fuji X100S is Fuji’s premium fixed-lens camera and features a unique sensor with 1.5X crop-factor, just like most DSLR cameras. It has a resolution of 16 megapixels which is maximized by using a special color-filter-array which does not require an anti-alias filter to avoid moire. This one add built-in phase-detect autofocus which, along with the usual contrast-detect autofocus, proves a hybrid AF system.
Neocamera just published an extensive review of the Fuji X100S. They highlight every different with the X100 for those you own one or previously considered it. While it may be very similar in terms of design, Fuji completely reworked the interior with the new X-Trans II CMOS sensor a new speedy EXR CMOS processor which lets the X100S shoot at 6 FPS.