I haven't used the K5iis, I shot the K5 for a couple of years. I got excellent results from the K5. There are a few things that were obvious limits and causes of frustration on the K5.
The AFC mode is nearly unusable.
The focus points are too large and undefined.
Processing on all levels is slow. From focus acquisition to exposure, to viewing a shot after exposure. Live view updates making long lens focus very difficult due to lag.
This thread is just taking more time to get through than I have, so I'm replying at this point. Every single point you made up to here is every single gripe I've had with MY K-5 (and I haven't bought a K-5II/(s), either, as I felt it was too much of an "incremental" upgrade and I wasn't sure if I could also make the MAJOR upgrade I knew was "coming soon" if I did. I'm still waiting for my K-3 to arrive, as I ordered the Silver LE, and I ordered from B&H, which appears to be LAST on Ricoh's delivery schedule (maybe because they sold so many?), so I can't speak for the K-3 from personal experience yet, however...
The K3 fixed those things for me. Noise levels are pretty well the same. I limited my K5 to 3200 iso and have my K3 set the same. I have shots at that level on the K3 that didn't need denoising when looking at the whole frame, as well as shots at much lower iso that have visible noise. The hard earned lessons from the K5 noise handling apply to the K3.
I have noticed the K3 getting colors in situations where the K5 didn't. Similar light, similar subjects, one has vibrant and visible colors, the other doesn't. The IQ is better I find on the K3. It may be the lack of aa filter, so the same may be true of the K5iis.
White balance is much better. My DA*300 on the K5 had a noticeable yellow cast, I did a few presets with a white card in various lights for correction. The K3 using the same software and same lens is right on.
Exposure is more consistent. The flash in my experience so far just works where it didn't on the K5.
My DA*300 feels responsive and accurate on the K3, where on the K5 it was an exercise in frustration. I figure I have what amounts to another 100mm of effective length with that lens on the new body.
I am taking shots that I didn't bother with. The K3 delivers where the K5 was an exercise in frustration.
Most of the things you address the K-3 is doing that you either had difficulty with or simply couldn't accomplish with your K-5 are the sort of things I've been looking forward to accomplishing with MY K-3, as well.
My K5 had sensor stains, and after the Pentax Canada repair shot did their magic, my lenses were accurate, the focus screen was right on. It wasn't finished at the factory. My copy of the K3 is right on.
So yes in my experience the K3 is substantially better than the K5. I can't comment on how it compares to the K5iis.
As to the K-5II, as I made a FIRM decision I wasn't going to buy one, I've never really paid much attention to all the talk on the forum about how they compared to the original K-5, except I have been aware they had sensitivity down to -3 EV (although they wouldn't necessarily FOCUS down to that level, I don't think -- I could be wrong -- from what I've read, the K-3 will also FOCUS at -3 EV), and, of course, that the K-5IIs didn't have the AA filter. The fact that the (II) series did NOTHING to address any of the K-5 focusing issues (didn't increase the number of points, improve AF-C, etc.) was perhaps my biggest reason for not considering it more, on top of not wanting to strap myself financially prior to the anticipated release of the K-3. Having read some (such as Mike) post, however, since the K-3 came out that the K-5IIs may actually have BETTER image quality in some regards, well, with the prices on those dropping, I may pick one up before they stop selling new (once that happens, prices tend to rise again -- original K-5 is now selling new for as much as or more than the K-5II again, because of its scarcity). Doing things in this order, if I do, I will have saved several hundred dollars, at least.
Finally, as to SBS and his original post (and the two responses he posted to photos posted by Mike and Greyser -- I read both threads), frankly, I agreed with Mike's response, at first. But now I see the issue. I've come across as "brusque" to people in the past, myself, because sometimes I've been too "direct." Some folks just aren't very good at being tactful, yet mean nothing derogatory by it. I suspect that's the case with SBS, at least I hope so. That seems to be what he tried to say in some of his responses above (again, I don't have the time to read any further right now). I see some folks in this forum who don't "get" humor, don't understand sarcasm, satire, parody, etc., and take a RIDICULOUS comment someone meant to be humorous at face value (maybe sometimes via a language barrier, but some folks really DON'T get humor. I've known a few). Some folks don't "get" tact. My late grandmother was like that... meanest woman you'd ever meet. NOBODY liked her, and I MEAN NOBODY, not even her own two sons... Only thing was, and I didn't realize this until the last time I saw her, just a few months before she died, she had NO IDEA she came off that way to other people. She just said WHATEVER came into her mind, with NO filter or thought of how it may affect someone else's feelings.
Actually, I think she had a mean streak, as well, but not nearly as bad as we'd all believed... most of it was simply she had NO CONCEPT OF TACT.
You live, you learn. Some folks just never learn some things.
Jeff