Can't speak for Quentin, but it's basically a myth, that some like to play in regards to older Pentax glass, not holding up to a modern 36 mp sensor. Older Pentax glass is just like older Canon or Nikon glass some work better than others. Try a 77mm 1.8 some time, amazing lens and a great carry lens due to weight and size.
As for the myth about current lenses, like 15-30, 70-200 150-450, again too bad that people feel the need to downplay these optics because they are re-worked Tamron lenses. I guess Tamron has gotten ALOT better. I can easily state, the Nikon 14-24/Pentax 15-30 are so close it's a hard to call, same with the 70-200. The Nikon 200-500 is still the best telezoom I have used, and the 150-450 is again very close. It might be that the newer Canon lenses are just superior to all other glass on the market, as I don't use Canon anymore, but I have plenty of experience with older versions of their 16-35, 70-200, 100-400 etc. Can't say any of these are "superior". I won't even get into the issue of existing Dynamic range and shadow noise from Canon.
It's a fact that the focal flange distance issue is a problem for many who don't want to switch and still use existing Nikon or Canon lenses, thus the A7rII has done very well.
But I guess I found:
Pixel shift, articulating LCD, better user interface, Astrotracer, Built in GPS, better high ISO, Built in Wifi, totally weather resistance for lenses and camera just to name a few things worth making the switch. The articulating LCD was really enough for me. I am tired of camera companies not adding this feature to a modern DSLR as just being to use a camera at waist level makes things so much easier, not to mention it just makes thing easier, period. As you grow old, you will also find that bending down to look at a LCD on a ground level camera is just not that much fun.
Now with the latest firmware of 1.3 EFC is coming as in the D810, and it might also be a full electronic shutter as this is used during pixel shift currently.
It's also too bad that DxO did not use Pixel shift in their testing as there is no doubt that the K1 would have taken the top score for 35mm cameras. The added resolution is no joke or myth, it's real and can easily be used outdoors even in mild wind. Pixel shift is real multishot and defeats the Bayer pattern interpolation, allows you to have a huge amount of resolution and takes much cleaner overall images. I have to give Pentax huge Kudos for working this out. I wish that Adobe would have spent more than 5 minutes are their raw conversion of pixel shift files. Based on the conversions I have seen from the Pentax software and Silkypix and Iridient, it's quite clear that Adobe left a lot on the table (Pentax should not have allowed this). With Phase One, not sure if they ever will support the Pixel shift files. They won't make any statement yes or no but so far only support the normal raw. I have asked them several times, but they have been moot, so I figure the support is not coming. DxO is supposed to support the pixel shift file in the near future and have made a statement to that effect.
I agree that the Pentax support structure at least here in the US is weak and that is unfortunate. The repair process of having to use a 3rd part (Precision Camera) is not a great idea either. Ricoh should address this issue sooner than later but I don't see that happening anytime soon. Tech support in the US, is very weak, and I am still not sure if the folks on the other end of the phone even work for Ricoh. But I have also had my fair share of problems with Canon and Nikon in regards to repair issues, but their tech support both web based and phone based are superior.
Paul C