In the AtheOS desktop you will also find the 'Preferences' application, which it will help you modify some of the AtheOS default settings. You will be able to change keymaps, set font defaults, change screen resolution and select a different window manager theme or modify color themes for the GUI widgets.
By pressing ALT+F1..F12 you can utilize the workspaces (virtual screens) available in AtheOS. Each workspacce can have its own resolution and color depth, but a common background image/color.
Two additional, must-have, third party applications that any AtheOS user should download is Launcher, which considerably eases the process of launching applications, and Locator, a file find utility. AtheMgr is also a must-have, as it manages the killing of bad-behaving processes, which can be very handy at times.
The GUI is pretty basic, but it is fully functional. Its app_server is written in C++ and the AtheOS GUI API is also 100% C++ and object oriented. Being a web designer myself, I am always nit picking a bit about the visual stuff, so I could say here that the GUI could do with the help of a GUI designer. Font and Widget spacing, general aesthetics are far from ideal, but as I said, works fine. That's just more than enough for a one-man project, as AtheOS is. A lot of GUI-related classes have not been implemented yet, so several people who are porting or developing their GUI applications to AtheOS, are often bumping on limitations. Word has it that Kurt is planning to completely re-write the whole GUI part at some point.