Symbian OS provides a developer-friendly environment in which to build applications and can be a powerful element in developer decisions when designing solutions for AT&T and its customers.
The latest version is Symbian^3. The latest version introduces a new graphics architecture and UI improvements (like new touch menus). It includes the Qt framework with an advanced GUI to create web-enabled applications. This is the sole framework now to build Symbian^3 apps. This include Qt Creator as the IDE (and also integrates with Eclipse and Visual Studio). Details on Qt can be found at Qt Home.