14
I use revision control for just about all of my documents for any purpose.
I'm using Mercurial, so setting up a new repository in a given directory is a matter of a simple "hg init", which I found much less of a hassle than setting up a new Subversion repository.
I've also found that RCS is great in any situation where you need to sync files - I'm using that now instead of rsync for all of my syncing needs. It's also easier to make backups - cloning a repository to another location/machine/disk means I can just push the changes to that location, which is even easier with a default push repository. If you don't modify in the remote repo, then you don't even need to worry too much about setting that up other than the default.
One of the nicest things for me is that I can have syncing, backups or whatever on any system that I have SSH access to. (Well, if they'd install mercurial for me at Uni, then I could!)