It’s really late, but I finally updated the build on graphicall to 2.79 release. Also, now that the cyclic behavior (for now with old auto handles) is in master, I submitted the actual smoothing patch for review.
I have also had an idea to display the main modes of keyframe interpolation and handle types in dopesheet. To make it simple, the types are currently represented by drawing lines inside the keyframe diamonds, and there is no option to turn it off yet:
In order: Auto Clamped, Auto, Vector, Free/Aligned, Linear interpolation, Constant interpolation, other interpolation.
The motivation is that with smoothing you can do a lot with just keyframing and setting handle types to match situation, and that can be done in dopesheet; but while you can set the type, you can’t see it.