App Store developers can and already do offer discounts on their apps for specific periods of time, but the process of doing so had been entirely manual so far. With the addition of advance scheduling, it'll be easier for developers to plan their sale periods and spread the word accordingly. It'll also eliminate the chances of human error resulting in sale windows starting and ending sooner or later than planned.

You have to hand it to Apple's resilience on all things App Store. While the company refuses to make any grand sweeping changes about the things it takes the most flack for, it keeps chipping away at the App Store infrastructure slowly. Hopefully, these tiny little modifications and new features gradually make it a friendlier place for developers.