On every effect, if I click on a slider I can then move it in precise amounts with the left/right arrow keys on the KB. I can also highlight the number in the box and type in a new value from the numeric keypad. If I'm in a Value Curve window, neither of those options appear to work.
I assume the GUI for all curves, regardless of what they control, is the same screen. Would it be difficult to modify it to work like all of the main effect sliders and numeric value boxes?