I would edit the command to xscreensaver -no-splash
Otherwise, you may get the little xscreensaver splash screen on login when it starts up.
Be sure to install all the extra screensavers which are extra packages:
xscreensaver-data-extra
xscreensaver-gl
xscreensaver-gl-extra
rss-glx
rss-glx requires some extra steps, and contains some of the best
screensavers. After installing it, read the file
/usr/share/doc/rss-glx/README.xscreensaver to get them to work.