The release announcement opens with a list of the most important areas of improvement.
The feature of KDE 4.0 that received the most criticism was Plasma. It was rather limited in its functionality, while also offering a rather new and unique way of handling your desktop. This led to many misunderstandings, which would be addressed in KDE 4.1, such as panel resizing and the lack of proper desktop icons. These, and more, have been addressed in KDE 4.1.In my quick review of KDE 4.0.0 back in January, I wrote that "the potential is just oozing out of every pixel. Combine this with the various new and updated frameworks underneath it all, and it seems like the KDE project is building a very flexible and modern desktop environment, that will do a lot to bring the open source community to a higher level." According to the various reviews of beta and release candidates of KDE 4.0 around the web, KDE 4.1 does indeed deliver on a lot of its promises.
On a final, but sad note, KDE 4.1 is a special release not just because the KDE developers have high anticipations for it. It is also an important release because it is dedicated to KDE developer Uwe Thiem, who died of a sudden kidney failure earlier this month. Thiem had been a long time contributer to the KDE project, with his areas or work ranging from programming to educating users in Africa about the merits of Free software. "With Uwe's sudden death," the release announcement reads, "KDE has lost an invaluable part of its community and a friend."