If you switch the camera over to RAW mode, you are choosing to bypass the film color simulations. You can shoot both JPEG and RAW, but your hard drive will hate you for it. I shot for the first few weeks in RAW just to really try it out as that is how I shoot my Sony NEX 7. The Sony has beautiful, malleable RAW files that need very little work right out of the camera. In fact, those files sometimes have a little too much dynamic range and need to have the highlights or shadow detail dialed back a bit. Overall, the files are rich, Blacks are rich, colors are vivid, contrasty and detailed which is a great starting point.
The X100s is different. I find that the color is a little washed out, and the RAW images need a lot of work to land on something that's my style, but that's a drastic contrast to the JPEG files which are the exact opposite. So, a few weeks in, I switched to JPEG full time on this camera. My friend Aaron shoots his Fuji cameras RAW for pro work so I know that it's possible, but he also does some magic in Lightroom that is beyond my level of expertise.
There are certainly a few times where I wished I had a RAW file to work with when I didn't really nail the exposure, but it's rare...and it probably forces me to get better at my craft.
[Update]
Thanks to Jens Rhode's comment, I discovered that Lightroom has calibration profiles that match the Film simulations on the X100s. I've loaded 4 different versions of a photo below for comparison. Please note that I have not adjusted color outside of the calibration profiles. I just added some contrast to attempt to match the JPEG and a little more on my second RAW edit to bring out the detail.
I find that it's pretty close after adding the contrast curve, but I'm not particularly crazy about having to add this to every photo. I'm wishing there was a way for Lightroom to pick up the Film preset from the camera in EXIF and auto apply it on import. I'll probably try shooting RAW + JPEG for a few weeks and see if I find that there is a noticeable benefit.