Woo, now there's a question
It will take a brave or foolish man to answer, but seein' as how I'm a little of both I'll say how I see it
.
Now I reserve the right to be wrong here!
Basically it changes the force draw curve and acceleration profile.
The problem with a simple straight bow is that maximum force and maximum acceleration is all at full draw, if you imagine trying to get the best acceleration out of your car, you don't simply red line it and drop the clutch.
reflex will increase early draw weight, but due to the change in string angle can give less change at full draw. The effect is even more accentuated if the reflex is severe and the string touches the limbs (like hooked tips or levers).
The problem with it is you are always limited by the wood and the skill of the bowyer. The best design made with poor timber by an average bowyer will be worse than a basic bow made with good wood by a good bowyer.
As far as I know the actual maths and physics of how reflex works is beyond most of us, and even thos who analyse it tend to use simplified models.
A compound achieves the ultimate improvement of FD curve and acceleration, by getting the arrow to speed up smoothly at an increasing rate, low poundage at full draw gets the arrow moving and then the full force ramps up giving a smooth acceleration not the hard lick up the backside that a simple bow gives.
Anyhow, I've popped my head over the parapet to be shot at... feel free one and all.
Del