Well, you can't blame the Sony lenses as well for the strange way Sony compresses RAW. But those (Pentax and Sony, that is) lenses can be used on their cameras. Primarily. And if the bodies don't bring the lens' quality into the pictures, what else should do?
Did you by now check out the images in the link I gave you? They show that this particular lens is a little gem.
I count 4 cameras you listed: K-S1, K-S20 (didn't find that on Ricoh's product portfolio, there's a K-20D or a K-S2), K-3 II K-5 II. So 4 out of 10 will show the full potential? That's not bad. Hope it's buyers know which camera they should choose. At least, it's the best for all bodies just not all bodies will show it.
The K-3, K-3 II, K-5 IIs, K-S1 and K-S2 have no AA filter AFAIK.
One of the issues of these lenses is build quality. But it is not only PentaxÂ´s or RicohÂ´s problem. Unless going for Sanyang [murdering the spelling, I know], most AF lenses have increased their price heavily.
For that, you need to go for the older FA lenses, if you can find them.
Not that easy to come by.
And the AA filter... it is true. That is the reason, usually, that the Canon-Nikon photos appear to be more liquid, more detailed.
Pity that Cosina is no longer having the "opportunity Voightlanders", those old fashioned marvels.
And Pity 80Â´s are no longer coming back. I did really liked the Pentax old 80Â´s desing approach to lenses, from those metal tanks of macro to the petite 50 1.4