Cumprindo o cronograma, saiu ontem o KDE 4.1, a primeira versão da série 4 para os usuários que gostam de testar novidades. Ainda faltam coisas em relação à série 3.5.X, mas já deve dar para usar no dia-a-dia.

K Desktop Environment - KDE 4.1 Release Announcement

While KDE 4.1 aims at being the first release suitable for early adopting users, some features you are used to in KDE 3.5 are not implemented yet. The KDE team is working on those and strives to make them available in one of the next releases. While there is no guarantee that every single feature from KDE 3.5 will be implemented, KDE 4.1 already provides a powerful and feature-rich working environment.
Note that some options in the UI have moved to a place in the context of the data they manipulate, so make sure you have a closer look before you report anything missing in action.
KDE 4.1 is a huge step forward in the KDE4 series and hopefully sets the pace for future development. KDE 4.2 can be expected in January 2009.

Rola um problema com o Xrender e os drivers proprietários das placas Nvidia, mas o pessoal do KDE diz que a solução não é com eles.

K Desktop Environment - KDE 4.1 Release Announcement

Users of NVidia cards with the binary driver provided by NVidia might suffer from performance problems in window switching and resizing. We've made the NVidia engineers aware of those problems. However, no fixed NVidia driver has been released yet. You can find information on how to improve graphics performance on Techbase, although we ultimately have to rely on NVidia to fix their driver.

Testei a 4.0 há uns meses... achei bem bacana, apesar de instável... Tô aguardando ansiosamente o pessoal do Gentoo incorporar a nova versão na distro...