KDE News reports that that KDE4.0 release has been pushed from mid-december to January. It seems that KDE developers want to solve couple of essential issues, among which were glitches in the visual appearance, and in Konqueror, such as before releasing.
Meanwhile, the progress towards KDE 4.0 is astonishing. Most parts, such as the KDE Development Platform and a lot of applications are considered stable and well-usable.
Some parts of the desktop experience do not yet meet the KDE community’s quality standards and expectations for a stable release. There are also some issues which need to be addressed upstream, for example a bug in certain codecs of xine that cut off audio fragments prematurely. The developers are confident to be able to release a more polished and better working KDE 4.0 desktop in January. The changed plans involve releasing on January 11th, 2008.
I hope they don’t do a Vista here and release it before it’s ready. From what I’ve seen of KDE Preview(admittedly, from openSUSE 10.3) it was far, far from usable.