If the first beta of KDE 4.2 is any indication, then the final release of the popular GNU/Linux desktop should be the release in which KDE 4 comes into its own.
Featuring numerous small enhancements to system settings and standard applications, as well as improved customization and features on the desktop and panel, 4.2 is a significant upgrade by any standards. Codenamed Caterpillar, the release offers hopeful hints of the butterfly that is scheduled to emerge in January.
For both developers and users, this milestone has been a long time coming. When KDE 4.0 was released eleven months ago, it sparked a user-revolt when distributions shipped it before it was ready for general release.
Between the radical new desktop features and the lack of customization, KDE 4.0 provoked strong, even abusive dislike in many users. Much of the controversy died with the release of version 4.1, but a vocal minority continued to condemn KDE 4, comparing it unfavorably with the highly-customizable KDE 3.5.9. Now, KDE 4.2 offers a strong chance of silencing the remaining criticism.
KDE 4.2 is available as source code, or as packages for the openSUSE and Pardus distributions. Probably the quickest way to explore the beta is via the KDE Four Live CD available from openSUSE. As you might expect from a first beta, crashes are likely, and none of these sources is suitable for anything more serious than satisfying your curiosity.
The core programs in KDE have changed only in minor ways. However, going through them, you will find minor tweaks in many of them. General setup is enhanced by improved dialogs for configuring printers and PowerDevil, a laptop power management tool that longtime KDE users might see as a modern replacement for KLaptop.
Other notable features include a zoom slide in the Dolphin file manager, support for vi keyboard shortcuts in editors such as Kate and KWrite, and enhanced loading speed in the Konqueror Web browser. The changes to Ark, KDE's file archiver, are especially extensive, including options for password-protection, support for more archive formats, and integration into the Dolphin file manager. Such changes are relatively minor, but soon start adding up.
However, the most obvious changes in 4.2 are in desktop configuration. For instance, in earlier KDE 4 releases, one of the most controversial changes was the unavailability of conventional icons. 4.1 introduced Folder View, a floating window for icons, but the demand for a conventional desktop remained.
Now, with 4.2, you can finally add icons to the desktop by using the right-click menu for items in the menu. However, this change does not diminish Folder View so much as put it in the proper perspective -- you can add your favorite icons to the desktop, while creating Folder Views for specialized tasks, such as graphic design or audio editing, that you can call up as needed. You can now think of Folder View as the icon equivalent of virtual desktops.
For those who choose not to use a traditional desktop, Folder View itself is more customizable. While in earlier releases, all you could set in Folder View was the folder displayed and maybe filter its contents, in 4.2, Folder View has configuration options for setting the size, text, and position of icons, and for choosing a keyboard shortcut for opening each Folder View. The filtering of the Folder View display is also more comprehensive, and can be tied to specific file formats.
The 4.2 desktop has also over-hauled the available widgets (or applets, if you are a GNOME user). Developers can now write widgets in Ruby and Python, while the desktop will also run Google Gadgets.