Excerpt: Very nice compliment to the design and functionality of the X100s.A must for when you shoot with the filter and hood adapter attached which will otherwise cast a shadow in pictures taken with the built-in flash. I don't like the power button. I would prefer a lever-mechanical type button that you physically push into either the on or off position. Also the power button and LED should be on the side facing you and not on top. The LED lights are hard to see in sunlight.
Excerpt: This flash is excellent, if you do not exceed 10-15 feet in shooting distance. TTL worked as advertised and so did in Manual Mode. I keep this flash on the camera and fire it only when needed, but for serious flash photography, consider something else. This flash is very expensive for what its worth, but for convenience and with its small footprint to carry around, it is functional. This flash is great for fills and anything in close range.
Pros: Consistent Output, Durable, Easy To Use, Lightweight
Excerpt: It is good to have with you for fill-flash but be aware of its limitations: only GN 20, cannot be articulated when on camera. TTL function is good, but it is lost when used off camera (unless with a hot shoe cord). It's a good product but the price is outrageous. Well, sucker me,I bought one because I travel much and for that it is better than no flash. Also, Fuji camera is small so a small flash is suitable for it.
Excerpt: I love the ability to travel light with my Fuji X100s, and this flash is a perfect companion for it. My Canon kit (D5MkIII, big L series lenses, big flash) weighs a lot and takes a lot of space, so it gets left home a lot now that I have the X100s. The companion EF-X20 flash fits in a pocket so easily that it is an easy decision to bring it if it might be useful. I shot inside a dark cathedral last week with some weak ambient light.