UltraDefrag is very fast, because the defragmenting is done by kernel-mode driver. There are three interfaces to them: graphical, console and native. The GUI is very useful, because it represents your filesystem visually as a color coded cluster map.
 
The console is another option for those that prefer the command line. It is also allows you to run UltraDefrag from the task scheduler and scripts. Finally, the native executable will run at boot time in a manner similar to chkdsk.

The design of UltraDefrag is very simple. There are no skins and other unnecessary stuff. It is a small and powerful program.