Amen David, sermon over!

Wanted to stay out of this! Doh Cant!
For me I had a bit of a shock coming back to the K3, I initially found the noise pretty objectionable and was pretty narked about it, after being spoiled by the D610 and the Fuji X-T1 (Fuji crushes the blacks in it's film simulations, it won't look so noisy but then you lose a hell of a lot of shadow detail, the D610? Well it's a good sensor wrapped up in a peice of placcy crap, there I said it I've wanted to for a while and now it's out there...
Right then...

K3 sort of Vs K5 and K5IIs:

I upgraded from a K-5IIs to a K-3 (Via some other stuff...Well quite a lot of other stuff actually!) and if you pixel peep at 100%, there does seem to be a bit more noise, but it's luminance, not chroma. and it cleans up very well. The big caveat for me is hat I print and without NR you still would not notice it in print, (up to aourd ISO 1600) nor when posting photos online (Measurebating aside). I found the difference in apparrant noise between the K5* and K3 are greatly exaggerated if you shoot JPG. If you shoot RAW, then I prefer the K-3's noise as it is more film like. The higher dot count for the given area of the K-3's sensor means that you'll get a bit more noise, than the lower pitch of a K5*, it's simply physics! Pixel peeping is not the proof, your final output is, whether it be print or online, and in practice, you'll just not notice it.
In my own "very" indirect testing (I have never been able to stump up enough cash to own both at once, would still like a K5IIs...because I just like em!), the K-5 has worse chroma noise than the K3, which is harder to shift than luminance. With my K-3, (Notice I said "My" It's so good i've owned it twice!) I am happy to shoot in RAW up to ISO3200 and at a push 6400 before noise gets to be a big problem. Also, you need to take into account the K-5 (Original, Strong AA and a bit soft really in my book, your mileage may be different.) the K-3's RAW files require far less sharpening (if any) and that helps mitigate noise. K5II has a weaker AA but still needs a little sharpening, the "S" of course is filter free so the sharpening part of this little tale is a misnomer here! (Caveat with K5IIs wider Fstops, diffraction softening seems to appear at the same time as with the K3, well at least with my lenses, that were common to both cameras.) I pretty much do all of my PP in Lightroom 5, and I would have no problem blowing up any K-3 image shot below 1600 ISO 36"x24". Even 3200 ISO can be printed up to about16"x20" provided you are diligent enough with your exposure.
IMHO there is no doubt (Repeat IMHO!) that the K-3 is a better camera in every way to the K-5 series. Just shoot it in RAW and learn/find the best way to PP your images. Every camera model has its own intricacies and takes time to learn how to get the most out of your RAW files.
Recently I upgraded my old DXO-7 to DXO-10 (Sorry Algi I know you told me never to use DXO :blush and have been testing that a fair bit and I'm finding the RAW noise control in the Elite version (PRIME) to be a revelation!

Amen!
But I'm not going there with regard to the K3 focus system

eems to echo my thoughts on it really, the grip is too small but other than that it's not a bad little camera, except for the video bit, I have never and never will buy a camera for it's video spec but appreciate that some do, that being the case I don't think I could see a reason to look at a pentax at all?

Did say it was mobile, as was I, and thats where it works:
Heres the old fashioned stuck in the mud version:
http://www.pcmag.com/article2/0,2817,2470840,00.asp

Think it was this one David:

https://www.youtube.com/watch?v=1snZUq_X-qg


And the really interesting shutter noise test:

https://www.youtube.com/watch?v=wMrH9D2aQ_8

Not in front of the Pc at the moment but I'll correct that missing link later. In the meantime here's an actual review...

http://mobile.pcmag.com/?origref=http%3A%2F%2Fwww.pentaxforums.com%2Fforums%2F18...

Out for a K-S1 Walk
https://www.youtube.com/watch?v=jnw6a_jLd_8

Low light AF random "test"
https://www.youtube.com/watch?v=jnw6a_jLd_8

And how it sounds Vs others
https://www.youtube.com/watch?v=I7VNeguwZmA

Still reeling from your excellent red squirrels Alan, so it seems churlish to make cropping suggestions to a proper artist!
16X9ish to loose a bit of the empty foreground but not the sweep of the sand in 2 and 1 maybe to accentuate the curve of the chain, make it more important? However I do like the sense of space...
Belting shots whatever, I never get over there these days...Sigh