The ergonomics of the K-1 is superb. It feels very comfortable to hold in hands and feels very solid and balanced. The overall build of the K-1 is very good, but the camera top feels a bit plasticky and hollow.
AF is really accurate, but hit rate is not 100%, sometime it missed, especially when focusing in a hurry or under low light. But when it hits, it is really accurate. Tried the three FA Limited wide opened, no problem. Tried several other A, FA, FA*, DA and DA* primes, they all focused accurately wide opened. The K-1 probably is the most accurate Pentax AFSLR ever made, since the MZ-S. I really like it! :-)
Focusing is faster and quieter than before. But the speed is not particularly fast when it is compared to other FF bodies of Canon and Nikon. Forget about focus tracking with multiple AF points for moving objects, the points are still not enough and are too much centred. There is still some room for improvement.
Exposure accuracy is good, probably maybe a bit bright for its tendency, especially with film glass. Seems a bit more accurate with digital lenses. Nonetheless, the EV compensation is always there. It is quite easy to use with the quick function dial. I set it to +/- by default. Or, one can customise the e-dials to directly control the EV compensation.
Resolution of the images from K-1 is really superb. The per pixel sharpness is better than the Canon and Sony FF bodies that I have, even with the same lenses put on them. That's only my own subjective impression, though and no scientific measurbation has yet been made, because I am now busy with shooting with a good camera, instead of doing endless measurbation tests for faulty cameras.
Colour rendition is contemporary, which is now very Canon alike. It do taste very CMOS, the AWB is very white, maybe too white IMO than one would like to preserve the atmosphere even under the warm sunlight. But K-1 do really "catch up" with the game. ;-) I found it works best in the Natural mode, with the Saturation turned up one step.
Dynamic range is good, better than the Canon's. Noise is acceptable up to ISO 3200 and beyond that, use it unless it must be.
Lens correction now works very well. It is fast and there is no more delay as in older models, even with all the four corrected function enabled. Supported all DFA digital and FA* film lenses. DA lenses are supported in crop mode. Lens correction does not work in FF mode for DA lenses, even if they are actually FF compatible. On the other hand, for supported FF lenses, lens correction does work even when crop mode is selected.
Liveview operation is good, the liveview image will change according to the FF or crop mode selected (and of course). The LV AF is fast but unfortunate insensitive. It often missed focus with lower contrast, even under bright light situations outdoor.
There is nothing special for the video recording (movie) mode. And there is no live AF under movie mode. AF can be remeasured upon pressing of the AF button on demand by the user. It is not possible to capture any still photo during video recording.
The super articulated monitor is sturdy and easy to use, better than imagined before. Most importantly, the closed position is well aligned.
Mirror action is crisp but yet gentle, resemble the old feel of the MZ-S film flagship. The *ist D had similar feel in the mirror but however its movement is obvious too slow. Now the K-1's is quite good but I still hope that it could move faster anyway.
Viewfinder clarity is not as good as my Canon 5DIII which is brighter and clearer to see than the K-1, despite both have an overlaid LCD information display on the finder frame.
The electronic level indication is now very easy to see and follow. It is sensitive and accurate provided that you got a good copy. My first copy has good accuracy for the horizontal sensor but the vertical sensor is a little bit off.
GPS is sensitive and accurate and is very easy to turn on and off, with the dedicated button. WiFi is also easy to on and off with the special function dial. The red and blue LED indicators is a good design. However, the Ricoh Image Sync App is just a piece of junk, undoubtedly. It is difficult to use, with limited features and its operations are completely nonsense, even for the basic functions of browsing photos and for downloading.