I have been shooting the X-Pro for a short time now, and I find it does black and white quite well. I didn't buy the camera for it's high ISO capability, as I have been comfortably shooting 400 speed film for years, but now it seems that I have been missing out, high ISO capability turns out to be quite handy.
Focusing speed is not as quick as I would like. On my Leica M cameras I generally preset my focus and aperture, and simply shoot. Fortunately, the Fuji can be operated the same way, but shooting is still not quite instant. All that said, the X-Pro usually focuses fast enough, and, with a little practice, you can get perfectly focused shots quickly.
I have never been a fan of the M8, it looks something like a M film camera, but it is not. I shot an M8 at the same time I was shooting a Nikon D70s, and, personally, though the M lenses were better, the Nikon made better images.
I am still getting used to the X-Pro, but so far I see it as money well spent. I do like the Leica M9, and I have been tempted by it, but I'll stick with my film M4's for the time being, and perhaps wait for the M10.