Many of the images in these locations are taken with autoISO with a top limit of ISO1600. I'm now using ISO3200 as my autoISO limit with good success.
Some of these images were selected based just on the f/2 aperture so not all highISO images. But the combination of highISO and f/2 on the X100 yields exceptional results for a camera of this caliber. Note on the VFR images the entire trip to Venice Florence and Rome were shot with a combination of X100 and LX3. Not every photo op was possible with this limitation, but as you can see from the range of images, a lot is possible and for simple travel photography you can nail your memories.