It has been a little more than a month since you were able to install the latest and greatest KDE on release day. Today is another one of those with KDE 4.2.1 (codenamed "Cream") hitting the shelves.
Today, the KDE team announces the immediate availability of KDE 4.2.1, which is a recommended update for everyone running KDE. (If you are still on 3.5, do consider again upgrading to KDE 4.) 4.2.1 has a nice changelog for those that want to read something while packages are being downloaded.