The KDE 4.7 desktop features various improvements to the KWin compositing window manager including support for OpenGL ES 2.0 rendering and better performance, the Dolphin file manager has received user-interface improvements, KDM supports GRUB2 options, and KDE Marble now supports offline address search. There's also many bug-fixes and various improvements to other packages making up the KDE Software Compilation.
The KDE 4.7 release schedule lays out the final release as being on the 27th of July. This first release candidate was originally supposed to come on Wednesday but was pushed back to this morning. Read more in the KDE.org press release.