So its been a little while for me with the XE1 and I have only been using adapted lenses with it.
My thougths:
Focus peaking is not very useful overall as it is implemented in the camera. The Sony peaking is much better. Fuji's peaking turned up to high and using the viewfinder on the XE1 is barely noticeable in most conditions, on the back screen it is much easier to see, I can only imagin how much worse it must be on the Xpro1 with its lower resolution finder. I think it may be the compression of the pixels that is making it hard to see in the finder. Also having white is a poor choice for peaking color. It needs to be red or something else much more noticeable than white. As it seems all the peaking is doing is drastically increasing the sharpness setting in the preview and the white edges blend in too easily with things. In low light its useless. In good light its ok but because you have to have it set to high in order to see it through the viewfinder you have bad accuracy. Many of my shots were back focused because of this. Even at f4 or 5.6 I was missing focus at 10+ meters. You can use the zoom in function and focus that way but then your ability to capture moving things is pretty much gone. If you are trying to do street photography where you are doing more than focusing on a scene and waiting for something to happen or a person to walk through then you are not going to have a lot of luck with focusing.
As it stands now, focus peaking on Fuji cameras. No.
What Fuji needs to do to make focus peaking work is add different colors, different sensitivities, work out the problem where you cannot make out peaking very well in the finder, and maybe add some different patterns to the peaking algorithm like for instance instead of just sharpening things up 20x they could use color blotches or moving zebra patterns.