This lens is the Rodney Dangerfield in Fuji's lens line. Not the fastest, not the widest, people rush on past to the 14mm 2.8, or to the 23mm 1.4. Mistake. If you're a prime lens shooter, there's a place for a 28mm equivalent lens, and f2 is fast enough. I was gifted this lens - I too had rushed past it when building out my Fuji XPro 1 based kit, but since I received it as a gift, swapping it out wasn't an option.
First time I put it on was walking around in Las Vegas in the evening and night. Revelation time - it's small, it's light, f2 is just fine, and it's a great crowded street focal length. When I looked at the images later on, I was really impressed with edge to edge sharpness and contrasty saturated color. Shooting into the light (something I tend to do a lot) and not a single flare or coma showing. I ended up using the 18mm as my default walk around lens, only changing it out when the 14mm or 35mm were needed.
If you're just getting into the Fuji X series, go look at your past shots and see how much you shot between 24mm and 35mm. If it's significant, this lens is a great addition to your bag. What it gives up in extreme wide and extreme fast max aperture, it gets back in size and lightness. And its as stunning as the other X series lenses.
Bag 'o primes shooter? Gotta get this lens, it's a bread and butter focal length. Zoom fan? OK, walk on by... but with the quality of Fuji's lens line, you should be thinking hard about becoming bag 'o primes.
Pros: Sharp, light, small, contrasty, fast enough, core focal length.
Cons: Won't get you no respect, if you're a zoom person, it doesn't make great sense for you.