Well, congratulations on getting your K5IIs. I bought mine when they first came out, partnering a K7 after dropping off a K 20 D.
I must say I can only talk in superlatives about that camera (K5IIs) which was clearly quite a step up as a usable tool to the K7 which again is a great camera.
However, no sooner had I bought theK5IIs out came the K3 which I stretched my financial elastic to breaking point, ending up with a special silver addition (with drive).
I must say I use theK5IIs much more than the K3, and I am delighted with the camera in every way; it's quite easy to compare fine detail as regards functionality and specification but in my hands I would describe it as a real tool and the pleasure to use.
In the field I can't really see and major incremental change in the case three compared to the K5IIs, the sensor on the K3 gives a little more, but in practical terms it would have been sufficient to have swayed me now that I know minor advantage it gives when cropping.
However (again), being an “optical performance junkie” I have run fairly controlled comparison between the K5IIs and the K3 and frankly, whilst I can't describe technically what creates the slight reservation I have about the K3, (mainly because I don't quite understand it yet) I still reach immediately for the K5IIs.
As regards the AA filter discussion; after many, many pictures the Moiré has yet to register and when I first had the camera I carefully chose my subjects to put that potential issue to the test, now I am not concerned about it, it is just not a problem in a practical sense
However (for the third time) my reservations regarding the K3 are associated with a tendency it has to create extremely dense "reds” (I could have said oversaturated).
What is perplexing, is that this happens regardless of colour temperature, it doesn't happen all the time so there is another correlating variable I have yet to figure out
What’s more it is easily resolved by a post processing tweak.
I suppose if I wasn't comparing it to the K5IIs I probably would've tweaked it without giving it any more thought.
And as ridiculous as it may sound, I think psychologically seeing the “fancy silver livery” of the special silver edition (K3) when my usual photographic days are in fairly mucky and hazardous terrain I am tending to treat it it like I would when parking of a brand-new car in a busy supermarket car park, I don't want to get a blemish on it.
In summary I suppose I need a bit of K3 therapy, by using the camera as first choice, but there is no question the K5IIs is a tough act to follow and in no way is overshadowed by a K3.
So I am sure you will get great pleasure and satisfaction from the K5IIs; and having said that maybe my reservations (re the K3) is that it is very tough to create a camera after introduction of the K5IIs that would make me feel “wow what an advancement”
I probably will have to wait for the FF for that , in the meantime I am more than satisfied with the K5IIs and I am sure the K3 will do a good job for me, when I'm not reaching for the K5IIs.

Well, I must say I am using my k5IIs more than my k3 and there are some differences that I can see but don't quite understand yet; when I can put my finger on it I'll share a comment; the area of " raised eye brows" which is the best way to put it relates to colour rendition on the K3 which as of yet I can't pin down to a setting, it seems that under certain conditions reds are unnaturally saturated and very sensitive to tonal range and colour temperature, which would seem obvious but the reds are very strong when colour temperature at the high end ( not the " red end"so to speak) but I am not embarrassed to say it leaves me a little perplexed. Nevertheless it is a great camera but does not outshine the K5IIs at all, despite the sensor size difference and the very snazzy silver livery. I am sure it will continue to grown on me and maybe the jump from the K7 to the K5IIs was so vivid in terms of improvement I expected too much in looking for an improvement from the K 3 over the K5IIs, because it is not in anyway conspicuous, they are both wonderful to an old Pentaxian.

Already returned mine, works fine on primes but not on zooms where it needs some nifty double pressing of the shutter button to get a two stage focus on zooms.

Optically inseparable from Tamron but like all of them degrades the image and suffers CA too.

Tamron is smaller but identical on performance even though it is 15 years old. Very disappointed

Hated zooms until I met the 50-135 DA* and now the superlative 60-250 DA* (wow = I say it every time I see the results)

However, I described the 50-135 as the best lens I have ever owned - I have most of the DA* and an assortment of other Current Pentax and independents (Tamron / Sigma

The Pentax DA* was bought for me by my daughters when I had already aquired the Sigma 50-135 which was a nice lens.

The Pentax is in a different class, based on comparison of identical shots taken when I had both in my possession; from a handling standpoint they are both good but again the Pentax is nicer to use and frankly whilst I have read comments regarding it’s focussing speed; I have never felt it an issue and never seen the lens challenged.

The Pentax has a habit of growing on you and never ceases to remind me why I came back from a "Canikon" period.

And now, as I said above, a there's the superlative 60-250 DA*; wow is all I can say, and that is after my own evaluation against Prime DA* 200 and 300 on many, many field trips . It is simply as good a tool a wild life photographer can carry.

The 60 - 250 is not in anyway overshadowed by the 300mm DA* optically and is a complete pleasure to use.

People, who say "it's big" puzzle me too, take a look at professionals in the field or on the side of a soccer pitch. do they look as if size bothers them; they just want the best chance in the worst light hence ; the saucepan size lenses that deliver incredible images in dark cold drizzly environments.

Also in reality , overall the DA*s are not that big when compared to other marks of a comparative spec'.
Last year I took trip through Borneo and I met some guys who were very keen and excited to be there; whilst out "on orang-utans" one day they more than once commented on the size of the DA* 300 and the 60-250 zoom on a K5-2S which I had in a Tamrac Holster.


They were using more compact Canon lenses, remarking on the smaller construction and the fact they could get more in their bags.

However we were comparing pictures on a lap-top later one evening and they were stunned at the results from the two DA*s I was using; understanding that they were comparing more or less "entry level” Canons with the DA* lenses, there would be a difference but if the object of dragging yourself around the other side of the world into a deep and steamy ,” badly lit” jungle, why would you not take the lens for the job

Those guys were not buying the compact Canon zooms because of the price difference but because they wanted to reduce weight. An advantage they lost anyway by filling up their bags with several more lenses, lenses that were totally under specified for an expensive trek to Borneo.

Finally, I recently (with some reservation) bought the innocuous little WR 18 - 135, well, what a pleasant surprise; take a look at the little mouse in my portfolio, the little zoom is a very understated optic - great travel companion.

Going back to the very first topic – if you are a Pentax user and have a use for a 50-135 DA* don’t bother yourself with questions on it’s performance and handling, it is practically as good as it gets, as are all the DA stars, they don't have the "Star Rating" for nothing

Regards

Daronl