Not every 16-50 has problems. My 50-135 packed it in after 6 ½ years, but the 16-50 bought a week earlier is still chugging along. I like the f/2.8 all the way. On the K10 it was not the best for large prints, but on my new-to-me K3 it is hard to fault -- and focuses faster, too. It's still not a fast focusing lens, but in some situations the f/2.8 and the silent focus are helpful. It gives quite a bit of "bling" on a camera body with a grip and the lens shade on, too.

The 14 bit/12 bit increase does show up in difficult shots, but not so much in ordinary pictures. Indeed, the jump from 8 bit to 12 bit is huge.

The depth is 256 depths of colour for 8 bit (2^, which leaves very little room for adjustment. 12 bit (2^12) has 4,096 levels which is a huge improvement. 14 bit (2^14) gives 16,384 levels which is still a significant improvement when trying to recover shadow and highlight detail.

Pros buy Canon and Nikon because they can get a replacement to use while their cameras are being repaired, and the repairs take short times as long as they subscribe to the pro service contract. Pentax does not offer a pro service contract. You have to own your own spares.

Being an old curmudgeon, I don't need 108 fps to take sports. I wouldn't use a 7 fps on burst mode to take pictures of football games on a bet. I was allowed 72 frames for a full game - two rolls - when I was stringing. It was enough to get pictures good enough to publish. I was using manual Pentax without winder, and while learning, even preset lenses. I have quite a nice scrap book thank you. To print full page broadsheet, you don't need 36 mpx.

The resolution may increase on the sensor, but just how big do you plan on printing or viewing? My K10d (10.2 Mpx) prints 24x36 just fine, even with minor cropping. I would love a K5ii/s for the high ISO treatment. The K10 has a CCD sensor, and the colour treatment at low ISO cannot be beat, but CMOS is better at high ISO. Otherwise, the K10 is plenty good enough.

My K10d has slightly larger DNG files than PEF. Same bird, two formats.
PEF 15,183
DNG 16,596

The use of Velvia versus Kodachrome 10 (yeah, I've used it) versus Ektachrome vs Agfachrome (I liked it) is a form of manipulation, as mentioned earlier in this thread. The use of a filter is a form of manipulation. I got second prize in a contest in 1962 (I think) using a No 2 orange filter on a picture of the HMS Bounty replica on black and white film. It turned the exhaust fumes from her entourage into mist. I also used a Takumar 135/3.6 preset lens with its own additions to the character of the picture, and I selected an aperture that kept her and the mountains behind not blurred. This is also manipulation - not to mention the darkroom work to print it.

If one does not think that using film involved image manipulation one should merely select one of Anselm Adams' prints and find out how he did it.

I want a 60-250, but have a DA-L 55-300. It's tolerable, but f/5.8 sure makes for hard focusing at 300mm (AF worse than MF). I should have held out for a DA 55-300 so that I would have quick shift. That would save a lot of flicking of switches.

My standard take-most-of-it-all kit is DA 12-24, DA 16-50 DA-L 55-300, M 100/4 macro and M 400/5.6 plus AFA 1.7x.

On our last camping (trailering) trip I made a small kit in my LowePro AW 100 sling bag of just the 12-24 and 55-300. I was rather surprised that I did not have a big problem with the gap between 24 and 55. Very light, and as long as the light was good for the 55-300, quite useful. The second compartment carried the water bottle.

I still want every Pentax or Takumar (screw mount only) lens ever made, and would sell my soul for the FA* 200-500, but I wouldn't get all that much use out of it before my beloved sent my soul to its everlasting reward. Sigh.

My wife has the FA 24-90 glued to her MZ-S. Even on 24x36 mm frame it is quite good in the corners.

I can second the comment about using nylons as a soft focus filter, and the "Cokin type" filters ( I use a now defunct competitor's filters ) which are nothing more than a plastic sheet with a half inch diameter hole in the middle. The plastic is closer to translucent than transparent so the surround gives that glow to the sharp image transmitted through the central aperture.

Changing the f/stop on the lens controls the amount of glow transmitted to the film/sensor. Smaller f/stops restrict the lens' field of view to the hole, wider ones allow more of the glow from the translucent area to overlay the sharp image. The vaseline trick simply uses a clear filter to become only centrally clear with a glowy (?) surround, similar to the cokin type.

A soft focus lens such as the Pentax 85 has a number of smaller holes in a pattern that is exposed to varying degrees by the aperture, and thus changing the amount of glow added to the sharp image.

The stocking trick is not quite as good, although the effect can be similar, because there is no perfectly clear image area. I suppose one could cut a small hole in the centre of the stocking to increase the effect.

Pentax chose me. In 1961. There has always been a reasoned upgrade path with Pentax. I can still mount a screw mount lens, meter with it, and take images. My first Pentax was the first Asahi Pentax with the original 55/2.2 preset lens, bought used out of a pawn shop in Vancouver, BC, Canada. It lasted a long time, but the shutters (cloth) wore through, and I bought a KX (not the digital one) with K 55/1.8 and a Mount adaptor K. The original went to a collector for display in his shop. I could still use my Takumar 135/3.5 preset while saving up. And so it has gone over the years. A nice bit of used equipment here and there, and the next thing you know my camera bag holds a K10D with grip, DA 12-24, DA* 16-50, DA L 55-300, M 100/4 macro, M 400/5.6, 1.4X-S converter, 1.7X AFA, 50mm extension tube and in my wife's hands the MZ-S and FA 24-90. All my glass is Pentax. My choice and may not be right for you