The X100 sensor is traditional CMOS sensor, all later ones are Fuji's X-Trans sensor which uses a different pixel-pattern.
Personally, the X100 is the holy grail of a camera for me. I prefer the feel of the image to the same photo from 10-24mm at 23mm on X-E2. It is slightly softer, it is slightly more realistic to my eyes, colours are more true to life. Between all my cameras over the years, the X100 have taken more than half of all my photos and all of the photos on my wall are from this X100.
Yes, the autofocus is slow by today's standard, but still fast enough on latest firmware. The 2.0 firmware update bought it up to 5D mark 2 speed. Perhaps because I use it as my life's documentary camera, I don't do sports and I use AF-L when speed is needed, so I have adopted to its AF speed. (or you can say I never had a fast AF camera)
The X100F is very tempting. I've always wanted a joystick to change AF points, I really miss it from 5D2 DSLR days. Luckily X-E2 can be configured to use D pad, but my trusty X100 is missing this feature. The upgraded sensor is a bonus, allowing more crop during post-processing. T and F also adds hybrid viewfinder where a corner of OVF can be used to check focus, knowing Fuji's AF system, I feel this is a critical feature. So for me personally, T and F are well worth their price compared to S, which still has old X100 control scheme and only upgraded the sensor to something less pleasing to the eye.
But being a cheapskate, I'll continue to wait for the next one, so far changes are not worth the price of upgrade for me. (price as in money and loosing the X100 look)