What Changed in SwiftUI

Color Mixing: A new mix modifier on Color allows blending colors by a given amount.
Custom Shaders: Extended custom shader feature with precompilation to avoid frame drops.

Fine-Grained Control: New APIs for better control over scroll views.
On Scroll Geometry Change: React to changes in content, offsets, and content size.
Visibility Detection: Detect when a view's visibility changes due to scrolling.
Programmatic Control: More scroll positions to programmatically scroll to, like the top edge.
Additional Customizations: Options to turn off bouncing along a given axis, programmatically stop scrolling, and control content alignment.

Compile-Time Data Race Safety: New language mode for safer code.
Main Actor Annotation: Views in SwiftUI are now marked with the main actor annotation, isolating them to the main actor by default.

Accessibility Labels: Add additional accessibility information without overriding the framework-provided label.
Conditional Modifier Support: New accessibility features like conditional modifier support and app intent-based accessibility actions.

Dynamic Linking Architecture: Switch between preview and build without rebuilding the project.
Previewable Macro: Use state directly in previews, reducing boilerplate code.

Text Selection: Programmatic access to and control of text selection within text editing controls.

Gesture and Animation Integration: Use built-in or custom UI gesture recognizers in SwiftUI view hierarchy.
Animation Setup: Set up animations on UIKit or AppKit views and drive them with SwiftUI.

For a detailed overview, you can watch the session What’s new in SwiftUI starting at 14:17.