Ok, thanks for the reply, that is good to know. I don't hesitate to take your word for it. My main consideration is that the K5IIs has substantially better IQ than the original K5 in normal use. It is possible however, that the better IQ in both K5II versions can be, partly at least, attributed to a diminishing of the AA filter effect, since suggestions are often raised that the K5II has a thinner (lighter) AA filter than the K5. Bottom line for me, is that I have found the AA filter in the k5 too strong for my taste, from day one of using it. If the K5II dóes feature a lighter AA filter, it might even be to my taste. After all, I switched over to Pentax from Olympus, and Olympus had already applied a lighter AA filter to the latest body I used (moving from E3 with K5 style AA filter, to E5 with around 50% lighter filter).

Chris

With this statement I wholeheartedly disagree. I get consistent better results with the K5IIs and e.g. the Zeiss distagon 35/2 than I did with the original K5 and the same lens. Unless the K5II (which I have not used) indeed dóes have a weaker AA-filter and better working SR than the K5, there should be a consistent difference between this camera and the K5IIs, with even casual handheld shots. There is no need for controlled shooting, tripods or specific subjects, nor very large printing or 100% viewing, to get the benefit of the K5IIs.
My personal conclusion is, that no general statements whatsoever should be made on the difference/benefits between/of these two cameras. Much more sensible, is trying both out in your personal workflow and make a personal decision from here, knowing that the quality of your lenses, raw converter, monitor, printer and the way you view/print your images all play a significant role in estimating whether the K5IIs has extra benefits over the K5/K5II. That has nothing to do with any absolute advantage that only arises in particular circumstances, or only with a particular post processing. Nor should one forget that eyesight needs to be trained. With the right lenses, a raw converter like Adobe or Capture one, a calibrated quality monitor and/or a calibrated quality printer, there is a consistent and obvious benefit to the K5IIs. No intensive testing or much controlled shooting needed to see the difference, but even with the best of equipment, your eyes may need some time to start discerning the finer detailed images in normal view. I mean this as a general statement, not directed at you, but developing eyesight with regards to photography, is just as important to me as spending a lot of money on expensive equipment. I have no doubt however that the K5II is a wonderful camera

regrads
Chris

Thanks for these efforts, it may add to awareness of the differences of these two Pentax cameras.
I can only say that your conclusions so far are similar to the conclusions I have come to by simply using the K5IIs for half a year after having used the K5 for over a year. I use it with highly resolving Zeiss ZK lenses and the K5IIs can simply take more advantage of the Zeiss' resolving power, giving highly detailed images with minimal artificial post processing (deconvolution, sharpening).
The (much used term) "clarity" i.m.o. is boosted on the K5IIs by the clear transitioning of out of focus areas to in focus areas, giving more natural depth to images.
All in all the K5IIs makes more natural (less processed) images possible, and this can add to the quality of the images, of course depending on the quality of the lenses. Not necessarily every lens looks better on the K5IIs, but high quality lenses make images possible on the K5IIs that I at least was never able to get with the K5. That doesn't mean though that K5/K5II images could not achieve the same "sharpness" as K5IIs images with artificial means, but then, "sharpness" is a relatively limited term to begin with, and doesn't necessarily describe image quality. I should add though, that I never used a K5II, and I wouldn't want to imply that the K5II is not better than the K5 IQ wise. Speculations are common implying that the K5II inherits the weaker AA filter of the K30 (weak AA filters being a trend among almost all Dslr manufacturers). Also the SR may be silently improved, it seems this way at least.

Perhaps the frequent debates on whether the K5IIs takes pictures with higher detail than the K5/K5II or not, arise because people are using different lenses? And the many "test" pictures are taken with a variety of lenses.
I use the K5IIs with the Zeiss distagon 28/2 and 35/2, which I used on the K5 before I got the K5IIs. To my eyes, the images with the K5IIs are much crisper, and I cannot produce the same crispness and clarity from K5 raw files, no matter what sharpening routines. Especially the clarity that the K5IIs produces with the two Zeiss lenses is unique, and I quickly sold my K5. I have not used the K5II though, which is rumored to feature a lighter (thinner) AA-filter than the older K5, more on par with the K-30. I don't believe there are any official statements from Pentax itself on this though.
Anyway, I would advice anyone with higher grade lenses to at least try out the K5IIs for themselves, it is for me the first camera, that I will most probably not upgrade anymore, but simply shoot until it stops working. I think it's thát good.

regards
Chris