I've found this thread interesting. Some having great success with stevia and others none or very little.

I wonder if the inability to perceive stevia as sweet could be genetic. If the "sweet receptors" in the taste buds of the tongue are unable to be stimulated by the chemical configuration of stevia then one would not perceive the "sweetness".

Similar to someone not being able to perceive a certain color with their eyes.

Just a thought.