Every review site, and every person who's tested the drive has not experienced the "slowdown" claimed in that review.
As Ars said,
The fact that Intel felt it necessary to make public comment on the matter is significant in and of itself; and that they've tried to replicate the same results unsuccessfully, speaks volumes that
a) the PCPerspective testing method was flawed
b) The results are not indicative of what any user has ever or will ever actually experience
c) Intel is on top of their **** and investigates when someone thinks they've found a flaw in their SSDs in order to fix the problem if there is one