I tested 5 copies of the DA*55 and was unable to find one that could focus reliably on my K-7. I even tried one of them on a K-5 unsuccessfully. My experience is consistent with dpreview's test results. There are many satisfied users of this lens, so I believe that there must be some perfect copies out there, but I also believe that some of those users are simply unaware that their lenses are dysfunctional. (It happens all the time.) My advice to prospective buyers is to test the lens rigorously for focusing defects. If you get one that works, it should be great.