How are people using workflow?

I'd like to RTFM but there doesn't seem to be an M to R. Some real world examples of precisely how people are using workflow in production would be very helpful! It would eliminate a whole lot of confusion.

One of the things that I would like to do is to display a message to unauthenticated users posting comments (encouraging them to register). I am clueless how or, for that matter, if this is the right module to do that.