I photographed about four hours and by the end the camera battery was indicating low but not out - still functioning fine. I had used live view for all the images, and many were 30 second exposures inside one of the Turner Valley Gas Plant buildings, all the windows boarded up, light supplied by one large door in a very large building. I used the 25, 35, 75, 120 and 300 mm. lenses.
To my surprise, the images from the 300 look great - very sharp. This might have to do with the 30 second exposure eliminating shake, also no wind indoors. Outdoor images were inconsistent, some sharp, other very definitely showing movement. I know that when I was using both Canon and Nikon, 2 seconds wasn't enough to settle movement after pressing the shutter and I'm looking forward to getting an infrared remote for the camera. Clearly more testing is required, but it's nice to know the lens itself is fine.
The camera worked perfectly, with no quirks that I could discover. I'm still learning how far to the right I can push exposure. At the moment I'm being pretty careful not to go well into blown highlights just in case, and knowing I can dig into the shadows without problem.
My impression is that while resolution may not be that much higher than the D800e, it's easier to get high resolution - the Nikon could do it, but not consistently, even in similar conditions, and frankly that's a huge advantage for me.
When checking sharpness of an image already made, you can scoot around the magnified image quite quickly. When doing so in live view before the shot, it's fairly slow - not an issue for the kind of work I do.
Focus blending is working well, using Helicon Focus, and I made my first images today that will need to be stitched - which is perhaps a bit silly but the lens nicely fit the vertical part of the subject and it just seemed natural to then swing the camera.
I did wonder how badly I'd miss my zooms, after all my 70-200 has always been my favourite lens, both in Canon and Nikon. To be honest, I didn't even give it a thought till now, after the fact. Sure I did more lens changes as I set up scenes - but that's at least as much lack of familiarity with the angle of view of the specific Pentax lenses and already is improving.
I worry that the battery compartment lock seems flimsy - a thin tab that has to be lifted up, turned 90 degrees and then pulled to open the door. It would be very awkward in gloves. I'm going to be careful with this.
I have to be a bit more careful clamping the camera to the tripod head The small square Really Right Stuff plates are great for not getting in the way, adding bulk or weight to the camera, but as the camera is much larger than the plate, I seem to be spending more time checking to be sure the plate is really seated in the clamp before letting go - but this is mostly to do with the size of the camera blocking the view of the clamping, not the smallness of the plates and I wouldn't want larger plates. It's even worse when I use Arca Swiss style plates on a view camera. For that size, I actually prefer the safer and much larger plates from Manfrotto, but I wouldn't want to put two of those on the Pentax.
One thing that has to be considered with Pentax is the size of the company and the rate of development, though if you think of how long people have been waiting for a new 100-400 Canon zoom, or a 400 5.6 with IS, maybe I shouldn't worry too much. I do have the sense though that the camera and lenses have to work for me now, not from some future possible development. For my style of photography, the Pentax and its current equipment are perfect and I have no sense that I'm limited waiting for further developments. This won't be true for others, who might need leaf shutter lenses, or tilt shift. As to this latter, correcting perspective in Photoshop is so easy that shifting isn't really needed (and with the high pixel count, using shifting to stitch more pixels isn't important, and tilting has largely been replaced with focus blend, which is, after all, a lot more flexible being able to cope with 3D subjects, not just flat planes.
What if the company itself disappeared? People used Contax medium format for at least 10 years after the company went bye-bye, so again I don't see this as a huge issue and the fact that Ricoh can release such a great camera at this time speaks well of the company. The 645D was successful despite its limitations, the 645Z could be huge for the company.