It depends on the thumb stud (or other opener type as I prefer the SpyderHole) location on the blade, the blade to pivot position, your own thumb length and strength, and a series of other factors including familiarity with the tool in your hand.
An assisted-opener doesn't help me much because I deploy my folding blades with a four-step process. This sequence is done with a tip-up blade as most Benchmade knives tend to be of this clip orientation: 1) attain a thumb-behind the knife body and bottom-three finger grip on the pocket clip and handle (I place my middle finger inside the bottom groove of the clip for extra purchase and grip location orientation), 2) withdraw the knife from the pocket, 3) roll the knife up into a hammer fist with my thumb on top (I use this to steady the knife in the hand instead of the hip bump that mercop prefers), 4) deploy the blade with my thumb if necessary and I have time and space to do so.
As you can see, my particular sequence doesn't give me a way to effectively deploy a flipper of any type, AO or not, and with everything already lined up an AO will open the blade no better than my thumb is already doing so. Now add that my knife is a Benchmade with and Axis Lock and the ease of blade deployment makes it largely a non-issue where the extra gee-whiz of an assist really doesn't do me any good.