I absolutely agree and wouldn't be without CSF. The Server Security Check with recommendations about how to make the server more secure (see
this picture) is invaluable.
I hope you won't mind me adding to this thread a recommendation for another product from the same people -
ConfigServer Explorer. This adds a comprehensive visual file manager which is powerful and very easy to use. No need to use a shell or Putty any more; you can run linux commands from it as well - it's brilliant and easy to install. See the screen shots at
http://www.configserver.com/cp/cse.html. When it first came out I paid for it as it was so good but now it's free.