http://forum.photozone.de/index.php?/topic/711-pentax-18-135mm/
See what Klaus, owner/reviewer/editor of the PZ commented and wrote "preliminarily", a few quotes:-
"I'm sort of disappointed. I expected more from a 700EUR lens."
"The centering quality is alright for such a lens. Such a complex lens is never really perfect, of course. The field curvature at 18mm is an issue and the borders/corners at 135mm are just soso. This would be Ok ... if the price tag was lower. "
"The data does not suggest this. The Tamron 18-270 is also superior." (Someone asked if the DA 18-135 any better than the Sigma 18-125 HSM.)
The most mysterious thing is that Klaus told us that he planned to publish the review till the first week of March. But now time is approaching fall March. What went wrong actually? What's going on? :-o
Related:-
Ned Bunnell's (Official) K-5 + DA 18-135 Samples
No More Update at Ned Bunnell's Blog