Some of the eye-catching stuff are Swift UI and Catalyst.
Swift UI helps developers to build user interface in a declarative way.
SwiftUI is particularly interesting to me and, I watch most of the videos about SwiftUI. From Platform State of Union to Building Custom View with SwiftUI. I also built some experimental projects with SwiftUI.
The reason I am interested with SwiftUI is because it's seems the future's of how to build software's user interface. Declarative methodology has been used by React and Flutter already for their own platforms. Now it's the time for Apple making their own.
The benefit of using SwiftUI is we can build UI for all Apple platforms; watchOS, iOS, iPadOS, tvOS and macOS with same SwiftUI code-base, it will play nice with the environment the app will be used.
Catalyst is a technology to build macOS with the same codebase of iPadOS / iOS app. This will make developers easily port their iOS app into macOS. This will bring up new app to Mac App Store which is not as vibrant as iOS App Store.
Other stuff that also has been announced are iOS 13 and macOS 10.15 Catalina with performance improvement and new features. In addition, Apple also announced their new hardware for pro users which are Mac Pro and Apple Pro Display XDR. Those stuff are really expensive piece of hardware.