There is plenty of reason to shoot a fixed lens compact like the X100. It is a very capable camera, that a photographer who knows what they’re doing can probably achieve just about any shot they would with a similar camera.
What I’m saying, is that within its limitations, it is a great camera.
A $1600 6D with a $800 35/2 (my everyday setup) is not a whole lot more capable than this, but sure does cost a lot more. Yes, it is FF. Yes, it has cleaner high ISO’s. But those are the key differences.
The X100 is a TON more compact and portable, and should provide a more discrete shooting platform.
I’m looking at getting either one of these or an NEX-6 when I head to Korea in a few months, as a more comfortable street/travel camera.