I've now had a chance to take my new K-1 and D FA 24-70 lens on a short vacation that provided a number of photography opportunities. Before this trip, my K-1 shooting was primarily test shots with various other lenses, mainly to determine if I needed to buy the 24-70. I concluded that I would see a significant benefit from the 24-70 and purchased it just a few days before the trip. In addition to the 24-70 I also took the Pentax DA* 60-250 and the Sigma 8-16. I mainly shoot to capture beautiful scenery, but I'll take other types of shots when they are attractive to me.
The camera and new lens performed well during the trip. I took about 550 pictures over a long weekend. I was definitely impressed with the resulting pictures. I don't recall any missed focus shots that were not attributable to user error. I think the combo of the K-1 and 24-70 tended to overexpose for me a little and I found myself shooting at -.7 to achieve the exposure I desired. I missed having filters that would work on the 24-70, as my maximum filters are 77 mm and the lens uses 82 mm filters. I think the level of detail in the pictures is quite impressive, even shooting JPEGs. I think the color rendition was very accurate. With my K-3 I used the vibrant setting much of the time but with the K-1 I only used the natural setting. The SR was very effective. I used a tripod for longer exposures so I didn't really test the SR, but I had one shot at 108 mm at 1/8 second and there was virtually no signs of motion. I found the flexible screen very useful for shots near the ground, which were quite difficult with the K-3. I found the new screen brightness option very handy as I've struggled in the past to review shots on bright days. It was no problem to inspect a shot with the screen brightness increased. I used Pentax DA* 60-250 much more frequently than with the K-3 due to the crop factor. I was somewhat disappointed in the amount of vignetting that resulted from use of this lens, especially since I consider post-processing to be a chore. I didn't go beyond ISO 3200, but my shots at 3200 looked better than similar pictures with the K-3. I had planned to use and evaluate the on-board LED lighting, but I forgot about it since I felt quite comfortable with the K-1 in the dark because the controls are so much like those of the K-3. I did not miss the onboard flash on this trip, but I'm quite sure I will in the future. I did not use the GPS on this trip, but certainly will use it to embed location information on my pictures during future trips.
While I didn't feel that the K-1 was significantly larger or heavier than my K-3, the combination with the 24-70 is quite heavy. I used a shoulder strap much more than I would have with the K-3 / Sigma 17-50. I definitely didn't want to hold the camera very long, which was annoying at times. I was concerned that the K-1 and larger lenses would be a little heavy for my Manfrotto BeFree tripod, but it proved to be very stable. My backpack was definitely heavier than in the past with the K-1, 24-70, 60-250 and Sigma 8-16, but I must say the weight in the backpack never bothered me.
An analysis of the focal lengths I used during the trip shows the majority of shots with the 24-70 were at 24, followed by 70. For the 60-250 the most were seen at 250. This matches my prior experience as I tend to shoot at the extremes with my zooms, suggesting I should perhaps change lenses a little more frequently. I never used the 8-16 on this trip. Without going into crop mode the 8-16 is really only full frame at 16 mm. I will eventually have a better ultra wide option for this camera, but I'm still figuring that one out. I'd like to get the FA 20 2.8 if I could ever find one.
I did use the Synch Image app to transfer pictures from the K-1 to my tablet for sharing to social media during the trip. Like many men, I try to do everything without reading the instructions / manual first and this worked with a little difficulty for the uploads. The app is not very intuitive in my opinion, it worked but I found it to be a little challenging. Having looked at the K-1 manual today I see it would be pretty simple with the instructions. Overall, I didn't find the built-in WiFi to be any better than my prior use of an Eye-Fi memory card.
In conclusion, my trip experience confirmed many of the viewpoints previously shared by others. I saw many of the advantages and disadvantages previously discussed on this forum. The weight and need for full-frame lenses, which may be quite expensive or hard to find, are definite disadvantages. However, the IQ and extensive capabilities / features of the K-1 are big advantages. I'm very glad to have the K-1 and the 24-70.
The following sample pictures have not been edited except for resizing for posting (except the bridge shot was cropped a little).