in reply to Everything vs twiki vs ??
In my opinion the chief advantage of Everything is it is insanely customizable. By creating custom nodetypes you can do really complicated things which might be needed for a full content management system.
But it sounds like your users just want to drop something in and forget about it. In that case the simplicity of a wiki seems more attractive.
If I recall correctly, Everything requires a database while twiki doesn't. So backing up twiki is as simple as tarring up all the files and storing them elsewhere. It could even be done automatically out of cron