Digital Light & Color

Just a note before I forget; I've been reviewing software with lots of sliders, and it had a v. neat feature I thought: double-clicking on any slider set it back to it's default value. Cool, useful, global and doesn't take up any real estate in control windows. The only thing that may be even better that I can think of would be a functionality in which double-clicking on a slider the second time would bring back its last value: this way I could toggle before/after Preview, but just for this parameter.

There are several applications with this feature. I like your idea of returning to the last setting if you double-click again.