Hi Frank!
On a small note of this zoom, I basicly brought it for the sake of having a lighter load for travel. Seriously I did not know this zoom was quite a performer.
I shot plenty of landscape and aperture f8 would gaurantee landscape shots that you would not be able to see from any competition brands. The colour and contrast are just amazing! Actually, the wider the aperture, the better colour and contrast.
It is slightly weak in sharpness wide open in the corners (but narrow depth of field and front focusing to a degree). This is the area where quality control is an issue.
This zoom had been debated a bit in pentaxforums and I aggreed with some of the weakness of this zoom. f2.8 to f4 does cause a bit of inconsistent focusing. SDM is silent with no sounds fantastic for street candids but to get sharp shots using AF is a bit of luck involved.
For you Frank, the lens would be fantastic to use for protraits or candids. I shot food, people with the zoom and they are quite good in deed.
I still love Da14 and it is definitely sharper wide open. It is lighter and it is more capable to giving better AF. Though it gives a lot more flare than the zoom. Da 14 does not yield more colour or contrast than the zoom but you can bring all the colour and contrast out easily in photoshop.
This is really a great zoom to own (Tell me which competition brand has a zoom like this?)
BTW I walk through rain and tough weather with no concern over the whole k10d and zoom soaked with rain water