The facts are that nothing Samsung has done instills trust in them. Furthermore, the theories of what the issue actually is has never been put forth as fact by Samsung, only these same sites that proclaim the latest fix is godly have. And those sites I don't trust since last October because of this very fact (they miraculously figured out the reason of the slowdown for old files with their great theories).
As to the 'instant' upgrade in speed. I am even more skeptical than @Sheyster. Samsung has been known to fix benchmarks before and this would be old hat for them to do it here (simply tell the firmware to report the file as 'read', regardless of the truth).
For myself, Samsung has lost the little cred it had before, and it will be in the negative if this firmware proves to be as useless as the first one was and is for many. And no, I do not consider running the advanced optimization a 'fix' if the underlying firmware proves faulty. We already had MyDefrag and DiskFresh that handles that situation for us already.