I have a couple and they all serve different purposes. My main server is mostly used for file serving and I store everything on there. It houses all of my media files, documents, and almost everything I’ve done. Every couple of years, I buy a brand new hard disk (bigger of course) and dump everything on there. This same server hosts some basic web and ftp services so I can access it from wherever.
Internally, I have another server that’s used for development. This is where I test different web/app/directory servers and do programming work on it. I also have VMWare installed on it so that I can play with other OSes and load up different versions of different web/application servers.
So, they’re pretty handy to have.