There will always be ever so slight variations between copies of a particular lens because lens elements are made and assembled in batches. This is true irrespective of where a lens is made. Even though there is production automation, lens assembly still involves a considerable amount of human involvement and testing. As long as the lenses meet the QC limits, they should be fine. But like anything manufactured, there can and will be ever so slight variances between copies.
Independent testing is great, but even the most exhaustive on-line reviews and tests only test at most one copy of the lens. So given that lenses are made in batches at different manufacturing dates, can the so called reviews be really indicative of every copy of that particular lens. In philosophy this is the fallacy of generalizing from a single instance, so take those reviews with a pinch of salt.
The fact remains that a key Pentax representative has come out in the open to challenge the issue openly. Sure he could be saying there is no difference because he wants to assure Pentax users and has a vested interest to get them to buy MIV lenses. But then again he could have said nothing and allowed the unsubstantiated claims of the supposed superiority of MIJ lenses to circulate. Pentax shifted production but didn't change the product. Perhaps those who doubt his conclusions should come up with their own MIJ vs MIV tests because until anybody can come up with results otherwise, his assertions are pretty much there for everyone to see.
FYI local Prius owners also got recall. I should know as I have a friend who drives one.
http://www.toyotasingapore.com.sg/special_prius.asp
http://news.xinhuanet.com/english2010/business/2010-02/09/c_13169960.htm
http://www.asiaone.com/Motoring/News/Story/A1Story20100209-197697.html
http://www.cnngo.com/singapore/none/toyota-prius-gets-recalled-singapore-815099
http://www.straitstimes.com/BreakingNews/Money/Story/STIStory_488216.html