KDE 4.0 is finally going to be released some time in January - the current specified date is January 11th 2008 but I am willing to wait longer as long as the final release is as stable as the current stable version aka KDE 3.x. Now it might seem that KDE team is procrastinating the official release indefinitely. But I think all things said and done, it is much better for the project to take its own time and correct all the bugs in KDE 4.0 in its present form especially pertaining to the UI instead of trying to keep up with the deadline.
I recently tried the KDE 4.0 beta RC1 release packaged as a Debian Live CD and my experience as far as the user interface is a bit disappointing. Lets not get this wrong. KDE 4.0 for me is one of the most fascinating happenings in the Linux world. But in its current form, I faced the following glitches :
Sound was not working properly, some of the widgets could not be closed, then the sluggishness of the user interface is not something to feel ecstatic about. It has been officially told that the panel provided is not the final one.
On the positive side, I do like the new KDE menu which has had drastic design changes. It does take a bit of getting used to but the search bar on top of the menu makes accessing programs many layers deep much easier than in KDE 3.x. Dolphin file manager is quite good and Konqueror is even better than before. And then, most of the important changes in KDE 4.0 has been under the hood so to speak and these changes will definitely maintain KDE 4.0's lead as a cutting edge cross platform Desktop for many years to come.
