MIUI 9 on your device will be updated to its stable version. It's better than the Developer ROM you're using right now in terms of stability and productivity. However, here are a few points you should pay attention to:
1. Root access will be turned off automatically after you update. (And nothing will change if you haven't been using it in the first place). If the apps you use frequently need Root access, think whether you should choose not to update your device.
2. Stable ROM outperforms the Developer ROM in terms of stability and productivity. Moreover, it offers additional features (e.g., App vault) which were not available before. Note: Some new features might not be available due to compatibility or other reasons, but this wouldn't affect your overall user experience.
3. Your data won't be affected by this update. We still recommend to back up all important items to Mi Cloud or your computer before you start updating to avoid possible data loss due to abnormalities and unexpected errors.
4. Automatic updates will be turned off after this update. For next update, go to Settings > About phone > System update, and tap "Check for updates".
Optimization - Launching speed(07-01)
Lockscreen, Status Bar, Notification Bar
Optimization - Adjusted time for tapping the Lock screen notifications(10-24)
Fix - The search bar in the Notification shade wasn't displayed correctly(06-27)
Optimization - Folders open faster(07-10)
Optimization - Users can set their main Home screen in the editing mode(08-29)
Optimization - Multiple themes supported on the clock widget(10-19)
Optimization - Adding widgets to an empty spot with a single tap(10-31)
Optimization - Redesigned home page(08-24)
Optimization - Updated Peach blossom and Asphalt themes(09-14)
Optimization - Hide free and incompatible themes in the list of the purchased items(10-10)
Optimization - "Add to favorites" icon adjustments(10-24)
Optimization - Reduced the number of push notifications when the user is signed out(10-30)
New - Quick ball goes back to the edge after 3 seconds of inactivity(08-30)