in reply to My preferred version control system is...
I'm a sysadmin and I use versioning for two things: development and active configs. I use subversion & CVS for stuff I'm developing (slowly migrating to svn). I use bazaar for config files.
I have scripts that run every X minutes to check in any config changes into bazaar. This way, if someone else makes an edit or if I forget to do a check-in, I have a history I can play back. If I discover that some obscure web page stopped working 2 months ago (not unlikely, some people never check their own pages), and I need to figure out what I changed, my bazaar diffs are great. I almost never actually roll back, but it's a fantastic diagnostic resource. If someone says I broke the web server and I think they broke their own web code, I can show exactly what edits I've made in the timeframe in question. It's awesome.