The first good point is that it's free (released under the GNU General Public License). 2.It uses very little disk space (the download is 320kb, including documentation). 3.It doesn't have a setup program so can be put on a thumbdrive. 4.It's faster than most of the expensive programs. 5. Can be run from a command line to select more options than the gui and for inclusion in a batch file.
I also like that it can do a clean up before running as well as shut down the computer afterwards.