Fresh Curves has brightness, saturation and hue channels for more direct control on top of the usual RGBA.
Now it's possible to adjust on attributes based on another. Relative Curves also has a built-in preblur and a postblur curve.
Bezier cubic splines
with tangent handles for more curve control. Interpolation modes similar to the ones in the AE graph editor round things off.
Using invert you can work in your own color space. Apply your custom 'gamma curve', do the work and apply and the inverted one.
The integrated histograms helps you find and modify desired areas and gives feedback to your changes.
Tired of that old, tiny interface? Here is a big, nice resizeable one.
will come in handy for those out of range float colors or when fiddeling with details.
Edit and sample
Need to be precise? Just edit or sample your values. And change the color range to what you are comfortable with.