Ars technica provided a very extensive review of KDE4, which I though was a definate worth mentioning. I think everyone who switched to KDE4 or thinking about switching to KDE4 should take a look at this:
Some equally exciting additions in KDE 4.0 include the new Oxygen visual style, the Plasma desktop shell, the Dolphin file manager, the Phonon multimedia system, the Solid hardware layer, the Kross scripting framework, elaborate compositing visual effects, and the Strigi indexing system. The developers also performed extensive reorganization of the core KDE libraries to improve the platform APIs. There are so many new features that no single article could ever hope to address them all with adequate depth. For this review, I have attempted to narrow down the list and focus on a selection of core components. This article describes key features, evaluates various design decisions, provides insight into the developers’ long-term vision and enumerates some current weaknesses and limitations.
So check it out: http://arstechnica.com/reviews/os/kde-40-review.ars