Heavy multi-tasking kills your concentration. Get rid of distraction and focus on your current task. Let this tiny app emphasize the active window by fading out inactive ones.
I'm digging this app. It's kind of a cross between Mac OS X's normal windowing behavior and its (nearly secret) single-application mode.
I set the dimming intensity to 80% (the max), and the animation to .25 seconds. It's nice.
Update: Regarding single-application mode, a reader wrote to me with the following anecdote:
I actually forced my parents into single-application mode some time ago without telling them I did it. They actually don't know you can have more than one window open at a time anymore. I've never heard one complaint.