I'm basically an SLR shooter who tried, then fell in love with, an M6+35/f2 combo. 98% of the time I have a 35mm prime lens on both my D700 and ALL the time on my M6 (it's the only lens I purchased).
My whole reasoning for adding something beyond the D700, which is by the way the best overall camera I've ever used, was to have a light, discreet, fast camera for travel. One body plus one lens forces me to be creative and solve visual problems in the easiest way...move around with my feet. The drawback to the dSLR is which lens to mount to stroll with, and if there is discomfort with a single prime, then strap a big heavy zoom and then suffer the whole day, not including storage. Ever try to go to a nice dinner in a small, quiet restaurant with a big bag full of glass?
For me, the X100 simplifies the camera I now use to travel with...the M6+Zeiss 35/2 combo. If the lens is at least as good as I'm using now (a high standard, I think, but feasible after reading the details), there is not a good argument from a logical standpoint NOT to shoot this camera instead. I'm no Leica snob...the M6 is a good, solid, reliable travel camera. M8, M9...overpriced digicams which are too limiting for their cost.
The X100, as far as digitals go, has to be at LEAST as reliable as an M8 or M9, or any other non-weather sealed electronic camera. In fact, probably better versus the dust monster.
I'm not looking for man-jewelry to hang from my neck...just a travel camera that isn't image-quality limited. As someone alluded to earlier, it sounds like a D300 in a rangefinder body...pretty much exactly what I'm looking for.
Feel free to throw darts...it's sounds great to me.