The only time that the 23mm lens on the X100 isn`t razor sharp is at very close focus with a wide open aperture. Here`s a couple of substantially cropped shots of a rose centre, both shot at ISO 1600.
The first, shot at f2, is noticeably soft, but still quite acceptable. The second, shot at f8, is razor sharp.
|Fuji X100 - f2, no flash|
|Fuji X100 - f8 wé flash|
For the second shot, I ran out of light at f8 so I had to use the flash. Very close up the flash doesn`t perform well, cropping the top and bottom of the shot from light. I suspect that the bottom part of the shot was shaded because of the accessory hood adapter.