Which reminds me-
For an excellent example of how effective the use of a mirror character can be, Yesterday Upon the Stair is a must read.
I love how this character gets at things, so much more so than if Lois was just "thinking" them to herself.
Really interesting discussion, by the way.
the other CC
edit- you know it, had the belated thought that it might be helpful if I mentioned that this story is on the archive, is written by one CC Malo, and is one of the best things I've read all year. Go see.