http://www.photographyreview.com/cat/cameras/digital-cameras/digital-slrs/pe....aspx?TabID=2: For many serious photographers, pro and amateur alike, the K10D (GX10 equal/ my addition)stands on its own as a well-rounded photographic tool that can be used for many types and styles of photography. While some may take issue with the K10D's image quality, other photographers may not be as trapped by the endless pixel obsession cycle (see Ken Rockwell's "measurbators").
And more from Phil:
Pentax may well have been aiming for a smooth film-like appearance but I at least feel that the inability to tweak this out by increasing sharpness is a mistake. That said it's unlikely you'll see this difference in any print up to A3 size, it's a 100% view thing so you have to decide if that's important to you or not. To get that absolute crisp appearance you'll need to shoot RAW, and use Adobe Camera RAW or another third party converter (as the supplied converter produces similar results to the camera).
https://www.pentaxforums.com/forums/newreply.php?do=postreply&t=11817
Be careful of people that like to take things out of context:
And my own take on the issue:
After some pixel level examinations of the Pentax vs Nikon examples on Phils site the only difference I see (at the pixel level) is Pentax has a 1 extra pixel "smear". 1 pixel difference in edge sharpening. Unfortunately it seems to be quite "visual". As to the reasoning for the "poor" jpg's I think Klaus'es findings shed some light on it. Pentax did something quite different by using a "unbalanced" AA filter (something no other camera company has done, kudos for the "mold breaking" attempt). This "feature" allows for an increase in resolution of the RAW files but needs some aggressive de-sharpening in the jpg in order to eliminate any (most) stairstepping and moire caused by the weak to non-existant AA filter in 1 direction.
Pentax K10D Review / Test Report
......."Now is this something bad ? Not necessarily. You may argue that this is a design decision because the potential resolution is roughly 10-15% higher compared to other Sony-based DSLRs (Nikon D200, Sony Alpha 100). That's assuming you use a capable RAW converter naturally - the Pentax PhotoLab or straight JPEGs do not qualify here. As we've seen the extra resolution doesn't come for free. This is probably also the reason why straight JPEGs as well as PhotoLab RAWs are comparatively soft because Pentax decided to apply an inferior (I'll add that it isn't inferior, just necessary, but that's just my take on it) software low-pass filter here"................
Bottom line: Design decision value (good or bad) are in the eye of the beholder. Pentax said they wanted (my paraphrase) to build a photographers camera, not a P&S. That they did. They increased resolution at the expense of in-camera jpg's. From someone who refused to even "think" about a camera (pre-pentax) that didn't have RAW capability was nothing short of buying a Polaroid it didn't bother me the least.....................
If it's not broke, you can't fix it. BUT you can change it
YMMV
https://www.pentaxforums.com/forums/pentax-dslr-discussion/11747-k10d-softness-jpeg-3.html
Best to research this yourself.