Most desktops give you the option of selecting whether to play a sound or have a popup window notify you of different system and program events. KDE 4.2 not only gives you these options, but also the choice of logging events (which can help you to track problems), marking a taskbar entry, running a custom speech file, or turning off notifications altogether. If you are one of those who despise sounds or popup notifications, you should be able to find some option that satisfies you at Main Menu -> Favorites -> Configure Desktop -> Desktop.
Remember the single row command lines that main menus and file managers used to have? KRunner is their highly evolved descendant. Started by pressing Alt+F2, KRunner can be used simply for entering a command, but includes over twenty plugins for such tasks as doing simple calculations, converting from one unit of measurement to the next, spell-checking, and searching bookmarks, address books, and Konqueror's history.
Using many of these plugins require learning some simple syntax. For example, if you wanted to start a web search for Datamation, you would enter "gg:Datamation," while if you wanted to know how many centimeters there are in four yards, you would enter "4 yd in cm." However, the syntax is easy to learn, all the more so because of KRunner's typing completion.
KRunner also features a choice of command and task-oriented views, and a summary of all current running processes that you can use to kill misbehaving ones.
The best way to think of KRunner is as a main menu replacement for intermediate and advanced users. In many ways, it combines the flexibility of the command line and the ease of use of the graphical desktop, offering all sorts of utilities in a very small footprint.
Folder View is not the only part of KDE 4 that allows the quick loading of different profiles or sessions. If you look at the list of available widgets, you'll see that you can add widgets to launch different profiles of Konsole and Konqueror, and different sessions of Kate as well.
These profiles and sessions are basic when you first start to use KDE. For example, the only profile for Konsole in openSUSE is a root shell, while Konqueror's profiles include File Management, Web Browsing, and Tabbed Webbed Browsing. However, you can add new profiles from within each application, and use the widgets to save time by going directly to the one you want to use.
These are only the most basics for settling down to work comfortably with KDE 4.2. Probably, you will want to right-click on the desktop and choose Appearance Setting to configure your desktop wallpaper and themes, and to browse Main Menu -> Favorites -> Configure Desktop for other ways to tweak your system. But, in general, these tools differ little from earlier versions of KDE -- or from most other desktops, for that matter.
You will also find individual programs have been redesigned. For instance, Amarok now sports a very different interface, while the KDE-PIM suite now uses Akonadi, a common storage server that requires a MySQL database for storing information. Such changes will take some readjustment, and introduce many new concepts and functionality, but are far too numerous to mention here.
However, once you are aware of the basic changes mentioned here, you can set up a desktop on which you feel comfortable, and use it as a starting point for other explorations. KDE 4 has been a long time arriving and gaining acceptance, but, with KDE 4.2 it has finally arrived -- and, with it, lots to discover.