Oh why not write it down ;)
There's probably little use for espeak as a stand-alone application; you'd rather call it from another application for text-to-speech output.
But: It can be fun if you're into command line and SSH. It scares the hell out of your family if they think they're alone in a room and suddenly an unknown computer voice says: "Come on now. Why don't you finally stop watching this soap and start cooking?"
I had a good time until they found out what it was.
Seriously, though, i wish more applications would offer text2speech as an alternative output now the possibility is there.