Many reviews are essentially subjective, in which case one should make his own opinion about the reviewer's personal preferences, biases, etc. Parker comes to mind (for wines), or Björn Rörslett (for Nikkors), etc. I do not rely much on Parker because his findings do not really correlate with my *experience*; I do rely on the other one because the correlation is good (except for the 50/1.8 until I found a good copy of the long nose version).
My grabbing one lens rather another one does not depend on sharpness only, let alone on MTF curves. My perception of a lens seems to depend on the pleasing memory of having obtained "good" results - the final shot, after PP, generally not printed, in which case sharpness is only one ingredient, I dare say secondary one, with respect to all manipulations and to the final downsampling. On the other hand, sharpness and "good" results seem to correlate well, and that elusive "3D pop" notion too. This is why I am still fooling around doing comparisons by using real life situations, rather than charts that I find nearly useless - real subjects have a depth and are placed at various distances, and are not uniformly lit. Still wondering about what ingredients contributed to the success.
At least one ingredient cannot be traced back on the final shot, namely the ergonomics. I always felt comfortable with the 50/2 ZF2, to the extent it was my standard lens in Iceland two years ago. On the opposite side, I do not feel at ease with the 50/1.4 AIS because my copy has too loose a focus ring which, in combination with the relatively short throw, is annoying. Result is a lower statistical score of focus accuracy, so the ergonomics may express themselves in the results after all.
No Ken Rockwell bashing from my side. I observed a few strange findings making me wonder if he ever has the reviewed lens at hand, indeed, but the same holds true for more renowned reviewers with paying websites.
His theory that lens sharpness does not really matter sounds provocative, but his insistence on the importance of a good focussing technique is quite to the point. Many of my naive test attempts (partly) failed because of that.
The only thing that really put me off on his site is his theory that "made in Japan" means good, "made in Thailand" so-so, and "made in China" means bad. Too much stinky ideology behind. I experienced that QA (like democracy) can be put at a use everywhere. But that's for another thread.