It's not good to be better than the worst. The 5D is a very old camera. The AF challenges in low light are puzzling (this morning, at around EV 6 in daylight, it was pausing for 1/4 second before doing anything... which took a good second). In the same light, my D700 locked and focused in about 1/10 of a second - with a much slower, 15-year-old, 35-105 AF-D lens.
I think the point is right that the semiotics of this camera are that it is designed to be used successfully in low-light situations (I don't count concerts, for example, in this category because the lighting contrast makes it easy for anything to focus). Why do we otherwise care about noiseless performance at 3200 ISO or an f/1.4 lens - unless this is simply pitching to people who like to take night time landscapes or daylight bokeh pr0n (both of which functions are done better by things like the D800 anyway).
The point has been made by dreilly - correctly - that you can't apologize for the way something works by elimination, "oh, it's not a Leica," "oh, it's not a DSLR," "oh, it's not this," "oh, it's not that." It's in fact patronizing to suggest that people don't "get" what a camera is designed to do. Is it my lack of experience with rangefinders that's holding me back? Lack of experience with SLRs? Lack of experience with high-end compact AF cameras? After shooting with a variety of things for 27 years, what are people like me not "getting"? A lot of us don't have a place for a utility outfielder in a camera bag.
Feting the X-Pro1 based on image quality in very controlled conditions is like feting a gifted child for having a high raw IQ - in neither case do you end up with something super-successful. You end up excusing quirks that ultimately undermine the program. There is certainly no reason to hold back on holding Fuji's feet to the fire on the focusing - which of all the challenges here should be the most straightforward to fix, possibly even with firmware upgrades.
Dante