As well as general organization and functionality, KDE 4 also features a number of new programs, or revamped old ones. One of the major changes in the KDE 4 desktop is the Desktop Toolbox (AKA SuperKaramaba) -- although you might miss it because of the icon that indicates that the Klipper clipboard is running. Sitting in the top left corner, at first the Desktop Toolbox might seem as misguided as the side panel in Vista, taking away the increased desktop space provided by wide screen monitors by filling it with useless applications.
However, the Desktop Toolbox is more versatile than its Vista counterpart, being largely invisible until the mouse pointer rolls over it, and its applets or "plasmoids" (a name that needs to be lost in the interest of user-friendliness) can be resized and dragged around the desktop. The selection of applets varies with the live disk you use, but all should have enough selection for you to see the concept. Like the gdesklets and adesklets that they resemble, plasmoids seem unnecessary, given the existence of panel apps, but perhaps as they become more common and more varied, they will prove themselves.
Another change is the move away from using Konqueror as both a web browser and a file manager, and introducing Dolphin as the file manager. If you want, you can still use Konqueror as a file manager, but much of that functionality has been removed, making it a much less cluttered application. At any rate, Dolphin, which has been in development several years, has always been far more powerful than Konqueror as a file manager, with not only a default directory tree pane, but the ability to split and merge panels and to offer some innovatively useful views, including an indexed one.
Among the new applications are Okular, which combines separate document views such as KDVI, KFax, KGhostView, and KPDF into a single program. Support for Postscript, TIFF graphics, and CHM (Windows help files), annotation and collaborative editing tools all promise to make it an essential application for many users.
The latest incarnations of many KDE applications have not yet appeared, but most of those that have show small innovations. For example, Konsole has tidied up its interface, making history controls more accessible, while KOrganizer now includes a new gannt timeline view. And KOffice, technically not an integral part of the push to KDE 4, but undergoing its own alpha release, now features a much-needed set of drawing tools in main applications like KWord.
All the same, after spending time with the KDE 4 beta, two facts should emerge: First, the release is an incredibly ambitious and complex project. Second, despite the complexity, to judge from the beta, KDE has a high chance of realizing all the ambitions wrapped up in KDE 4.