KDE defaults to a menu confined within a single window. However, it also comes with a classic menu and Lancelot, which is best described as a compromise between the other two. All are available as widgets, without any need to hunt out an extension. KRunner, which is best described as a menu for advanced users combined with utilities and controls for running processes, is also part of the standard install.
Incidentally, this kind of selection is characteristic of many KDE features. For example, the System Settings window defaults to a series of icons divided into categories, but with a few clicks users can view the same features in the tree view that was standard in the KDE 3 release series.
Clipboards for cutting, copying and pasting must be as old as computing. Yet on most desktops, the clipboard of today is identical to the clipboard of twenty years ago.
The earliest users of Linux desktops were developers. One of the few remaining signs of this origin is the lack of desktop tools for developers. To this day, a surprising number of users load fonts specifically for LibreOffice, but not for the system as a whole.
As with the clipboard, KDE is the exception. For years, its system settings have included a Font Management dialogue. From this dialogue, you can install fonts for the current user accounts, or for all of them. It's a basic feature, but one that's essential for any design work.
Activities are one of the most under-sold innovations of the KDE 4 release series. Activities are a super-set of virtual desktops, each of which can be configured with its own icons and widgets. Instead of having one desktop, with Activities you can have as many as you want.
Activities can be arranged in several different ways. You can have a separate Activity for work, school, and home. Alternatively, you have one for each of your most common tasks, such as programming, playing games, or designing graphics. If you are a professional, you could have a separate Activity for each active client, each displaying a different directory. Some Activities can be highly organized, with specific launchers, widgets, and links. Others can be a dumping ground for material you mean to read later, or arrange as sources for an article or essay.
If you make use of Activities, look at the widgets you can add to your desktop to switch between them. You may also want to set up keyboard shortcuts, either so you can jump directly to specific desktops, or else cycle back and forth between them.
This list includes only the most useful features. I could easily have mentioned another half dozen minor features, such as Account Details that include password setup and shortcuts for the Konqueror web browser, or configuration mode that appears only when you unlick the desktop, preventing accidental changes.
The list also includes only unique KDE features. A few other features, such as desktop hot spots and on-desk widgets, were unique a couple of years ago, but are starting to appear on other desktops.
Yet even now, KDE generally offers more choices with features that are no longer unique. For example, Cinnamon offers four hot spots compared to KDE's eight, and offers two responses per hot spot to KDE's seven (twelve if you have hardware acceleration).
Similarly, while Cinnamon offers three desklets, KDE offers ninety widgets, ranging from standard utilities and monitors to alternative menus and links for social networking. And while Ubuntu uses a flashing icon background as launch notification, for years KDE has offered a choice of launch notifications, including the option to shut it off altogether.
Some users might consider KDE's options overkill. But you can pick and choose the ones you want and ignore the rest -- which is very much the point. KDE's perspective on innovation is to offer features that extend the desktop metaphor without forcing you to adapt them.
Still, even if you are satisfied with a traditional desktop, consider giving KDE's unique features a thorough survey. The odds are, you'll find a feature or two that will immediately become essential for your daily activities.