I'm on support at OSH Park and we're still seeing a sizable majority of Eagle boards, but KiCad is definitely on the rise. I've got the impression that a lot of folks have been turned off by having to get the daily builds, so I'm incredibly excited to see the stable release. I'm expecting we'll see KiCad come to parity with Eagle over the next year or two.
We're also working on being able to take .kicad_pcb files directly, in the same way we take Eagle .brd files now. In the meantime, I wrote up a page with some KiCad screenshots and instructions for how to generate the gerbers and drill files we need. [1]
The major issues we see can be solved by checking the Protel naming format option so we can detect layers correctly, and by putting the board outline by itself on the Edge Cuts layer.