KDE Software Compilation 4.5 features a reworked notification area, the Konqueror web-browser can now use WebKit as a rendering engine, the KWin window manager now supports tiling, and according to the press announcement, "thousands of issues have been corrected."
On this KDE tech-base page is also a list of the different 4.5 feature plans for the KDE 4.5 software components and their current status. The items range from Kopete picking up Jabber Jingle video support to a bookmarks widget for the Plasma desktop.
The KDE SC 4.5 release schedule is available via this page. The second beta is expected on the 9th of June while the KDE SC 4.5 release candidates begin on the 23rd of next month.
The KDE SC 4.5 Beta 1 announcement can be read at KDE.org.