Windows tidy is quicker and more flexible than El Capitan OS’s new multi-tasking features. The main advantages are customizable configurations for how you want to arrange your windows (split screen, quarter screen, left/right or top/bottom, etc.). There are also no application restrictions, e.g. Microsoft Excel will not go split screen under El Capitan’s built in feature, but obeys Window Tidy’s command immediately.
Prior to El Capitan, this app was a must. Now, I might give pause to spend $8 unless I wanted more flexibility than just left/right split screens, which Capitan can do for most apps. That being said, this app is still a great productivity booster and would be perfect if it were, say, $5.