At first, the phone really does fly. Then the days go on. Days turn into weeks. Weeks into months. Along the way, the effect starts to deteriorate. My phone was being obnoxiously laggy for no reason whatsoever. Then I undid OCLF to update to JI6, and realized how much less laggy it was, even before I downloaded the update. So, yeah, it works, and it gives you awesome Quadrant benchmark scores to show off to your friends, but it doesn't last forever. It's by no means a permanent fix.
I now have a replacement phone with all my apps and settings just as they were before, and just rooted, no OCLF. The phone runs great. I don't plan on applying OCLF anymore.
Bottom line is, if you feel your phone isn't performing up to par (a lot of unresponsiveness, stuttering, etc.), go ahead and apply the fix. It's as easy as hitting "Fire It Up" and waiting 10 minutes. Just don't be surprised when after a while your phone feels slower than it was before the fix.