New KDE Applications, Workspaces and Development Platform Releases Bring New Features, Improve Stability Plasma Workspaces Become More Portable Thanks to KWin (*) Updated KDE Applications Bring Many Exciting Features Improved Multimedia, Instant Messaging and Semantic Capabilities in the KDE Platform New Instant Messaging integrated directly into desktop Stability As Well As Features More details in the announcement.
(*) A few highlights from the Plasma Desktop and Plasma Netbook 4.7 release announcement: More in the announcement.
Yesterday I did the upgrade to 4.7 for my Kubuntu 11.04 system without any problems. Looking good so far.