The feature of openSUSE that is most distinctive is YaST. YaST (Yet another Setup Tool) is both the installer and a complete configuration tool for all the most important features of the system. YaST is designed in a modular way, when used for system configuration tasks, it loads a particular module according to the task being specified.It is also possible to run a particular module separately without loading the entire YaST menu system. YaST can be run both in graphical mode and in text mode (generally known as ncurses interface).Although the functionality in either mode is identical.

YaST has always been the distinguishing feature of SUSE Linux, and it has grown organically with the SUSE distribution. In earlier versions, YaST was a monolithic program(working on a same block namely no modular working which has its own disadvantages ) with the release of YaST 2 it became modular. Traditionally the YaST license has been a controversial issue YaST was released under a license that, although it made the source available, restricted redistribution of the program by third parties. Due to which it is illegal to resell unofficial copies of SUSE CDs.
At the Novell event in March 2004, Novell announced that future versions of YaST will be released under the GPL. This change was first made in SUSE Personal and Professional version 9.1.

The best part of YaST from a user perspective is that we can do almost all of the system configuration using YaST only.
some of the features which i personally like are-
-we can change the bootloader entries directly from here without any headache of boot file editing or using  commands in terminal
-all the configuration of network devices and services( whether it is ISDN or modem or anything else) can be done from here itself
-software management ,addition of repositories ,package addition and searching is really easy
-hardware devices (printer,infrared devices ,tv card…) can be managed from YaST itself
-and other the other things like user profile management ,local security,firewall,languages etc.. can be altered and controlled using one thing only that is  YaST