KDE just gets better and better. Here's some of the major changes (the change logs indicate hundreds/thousands of bugs squashed).
KDE is delighted to announce its latest set of releases, providing major updates to the KDE Plasma Workspaces, KDE Applications, and the KDE Platform that provides the foundation for KDE software. Version 4.7 of these releases provide many new features and improved stability and performance.
Lots of visual polishing took place with an update to the Oxygen icons, and improved consistency between panel items such as clock and notification areas. Recognizing the modular nature of KDE software and the ability to mix and match applications from many different sources, KDE has also improved the Oxygen GTK themes, making applications from GNOME (and other applications using GTK+) blend seamlessly with KDE applications in your Plasma Workspace.
KWin now features an option for application developers to suspend compositing when a fullscreen application calls for it. This should increase performance for OpenGL games and GPU-accelerated video playback.
The Plasma Workspaces window manager, KWin, has received extensive cleanup of its code and can now run on OpenGL ES supporting hardware, making it better suited for mobile devices, and also improvements for desktop users. KWin has a new shadow system, improving support for users of older hardware or hardware for which driver support for OpenGL is limited (Xrender backend). KWin's performance improves noticably thanks to numerous optimizations in certain painting operations.
Plasma's Activities have seen many improvements, the Activity Manager now takes a more prominent place in the default panel in Plasma Desktop. Activities enhance the users' workflows by providing smart ways of grouping applications, widgets and documents.
Dolphin, KDE’s file manager, has a cleaner default appearance. The menu bar is hidden, but easy to reach and restore. The file searching interface has been improved. In addition, Dolphin now has much deeper integration with source code management systems, including the ability to create and clone repositories, push and pull changes, view diffs and much more
The semantic desktop components of the KDE Frameworks have improved functionality and stability. Nepomuk has undergone massive internal changes making it more stable and faster, with richer APIs for applications. Strigi analyzers now read meta-data in their own process, resolving over 35 crash-related bugs in Dolphin and Konqueror.