I shoot an M on film, but I would never consider an M8 or M9. Holding them put the choice in stark terms. The M3-M7 are just right in the hand. The M8 and M9 are just... wrong.
I will reserve judgement on the X1 until I hold one, and see how it does WRT shutter lag and focus speed/accuracy. The X100 was darned close -- the finder is simply amazing -- and the files it produces are remarkable. The X100's out-of-camera B&W files just crush the B&W I've seen out of the M8 and M9. They have a recognizable tonality that looks absolutely fantastic, like well-exposed ACROS developed in XTOL.
There's every reason to think that the X1 will be as good or better.
And the work I'm seeing done with the X100 is generally (though not always) much better than what I'm seeing done with the M9. This suggests that while the M and X100 may have slightly different limitations, the X100's limitations are not more practically significant than the M9's limitations. Note that I don't own either camera (again, I shoot mainly film, mainly with an M6).
The only compelling argument I can think of for an M9 is that it's FF, but at that price I'd rather just get an APS-C body and adjust my lens line-up correspondingly.