Regarding the AF on the X100, it's going to have to be stellar in order to outperform that of the Lumix G1 with 14-45 lens, or even the 20-1.7 pancake; with which I've spent the last two years doing street photography.
I would also say that, through my recent digital street photography experience, I really love using a well-designed EVF (like that on the G1), and am not certain if I'd ever really enjoy "going back" to an optical VF; I've learned to demand accurate framing in my images (I prefer not to crop) and any parallax error in an optical VF I find unacceptable.
So, I'm watching the X100 developments with interest, but am not ready to ditch (or supplant) u4/3 until I see the X100 offer distinct advantages, without losing the things I already like about u4/3.
~Joe