I got the used camera and have had it for a few days now. Used it a little but still far from learning how to use it optimally.
First I checked the firmware, since Fuji have been updating it since launch. The one I got had 1.21 installed, which is quite out of date. A few moments later I put the latest 2.01 on it.
Being primarily a Canon user, with a dash of Sony on the side, the controls took some getting used to. I wasn't used to having an aperture dial, and with the lens being so thin I found it a bit fiddly to reach. I also found myself holding the body like a compact camera, which meant my left hand obscured the OVF! I'll have to stop doing that. I don't find it natural to hold this body SLR style since there is not really anything for the left hand to hold onto, lens wise. I know I can control aperture or focus with it, but for now I use AF and either A mode or fixed f/2 or f/8 which covers pretty much all I need (so far).
I'm not sure about the position of the AF point selection button, as that requires the left hand to select, and right hand dial to move the point. The direction control on the right feels pretty horrible with a mushy feeling press, about the same as on a Sony compact. I haven't looked into if these buttons can be remapped or if there are some alternate controls for it yet.
Focus speed was never going to set the world on fire but in normal mode it is fast enough with the latest firmware. Accuracy seems ok although I do have a few shots at close range where the background seemed more interesting to camera. If you want to shoot really close, you need to go into a specific macro mode. The AF in macro mode is noticeably slower. I need to look up where the transition between normal and macro modes are, as I've lost some shots from not engaging it. I wish it covered both ranges in one seamless range, but I guess that would slow down normal AF speed too much. At least give the option to allow that.
Jpeg image quality is generally pretty good straight out of camera. It does a nice balance of sharpness, colour rendition, and highlight preservation. I've not really tested it at high ISO yet, but previous samples suggest it should perform well there. It may be a bit early, but it could be the best jpeg engine I've seen so far.
The only thing is, I think they use a higher compression rate than Canon or Sony as I can see macro-blocking effect in areas of high detail, which I don't on the other camera jpegs. I just noticed, all the jpeg files I have from the X100 are around 2.4 to 3.1MB in size. The 7D output is typically around 5MB in size, but allowing for the MP count difference that's about the same ratio. However, on the 7D, file sizes aren't all close to 5MB, with a quick look they vary from 4 to 7MB depending on complexity. I have to wonder if the Fuji is targeting a consistent filesize output, which means quality will be degraded for high complexity scenes. The 7D jpegs are more constant quality, so you get variable file size with complexity.
I haven't had a good play with raw files yet so can't comment on that.
Canon DSLRs: 7D2, 7D1, 5D2, 1D, 600D, 450D full spectrum, 300D IR mod
Lenses: EF 35/2, 85/1.8, 135/2+SF, 70-300L, 100-400L, 100L, MP-E 65, EF-S 10-18, 15-85
3rd party: Zeiss 2/50 makro, Samyang 8mm fisheye, Sigma 50/1.4A, 150 macro, 120-300 f/2.8 OS
Compacts: Sony HX9V, Fuji X100.