Expo is fine if you remember that there is such a thing as + expo and - expo (positive and negative). The curve should look like the picture below. This (positive expo) softens the initial input so that "a lot" of stick movement produces little control surface movement.
Then more to the stick end stops produces more pronounced movement of the control surface. The percentage is what produces the curve.
Many pilots say to set that to between 20 to 30 percent of positive exponential.
If the curve goes OUT, (negative expo) this is not really recommended for new pilots. This means that you have a LOT of initial input and less towards the stick end stops. Makes it quite a bit squirrely. I can't imagine an application for negative expo, but I'm sure someone out there has.
The below comes from the Spektrum DX7 manual:
Exponential is available for the aileron, elevator and rudder channels. Expo values are adjustable from
-100% (full negative expo), LIN (linear), and +100% (full positive expo). The factory default settings for both the
0 and 1 switch positions are LIN or 0%. Either switch position may be selected to give any desirable EXPO rate
by placing the switch in the desired position and adjusting the value accordingly.
Note: A negative (-) Expo value will increase sensitivity around neutral, and a positive (+) Expo
value will decrease sensitivity around neutral. Normally a positive value is used to desensitize
control response around neutral.
CGr.