Imagefoundry: I've bought a Pentax-K adapter for my Xpro1 off ebay and spent an afternoon playing with my collection of Pentax glass. I can sum up the experience as follows:
1. manual focusing with X-Pro1, combined with manual aperture control, is plain painful. Until someone comes up with an adapter than can change aperture on Pentax-A lenses (fat chance, as this requires firmware support) I wouldn't touch this again.
2. The whole manual focusing approach needs to be re-thought. One, I would like to see a detail window at all times, not full-frame, and not just when I press a dial (which is awkward in itself); two - the focusing detail window needs to be stabilized.
Pentax is awesome for MF focusing, from the focus peaking on the K-01, to catch in focus on the K5. For the latter, I just hold the shutter down, focus the lens and it snaps off the shot and the sharpness is fantastic, even at wide open on some relatively shallow DOF lenses.
We need XD cards to come back.