I'm with Windhover Weaver on this one, I've never had a problem with anyone using any form of aide memoire as long as it does not detract from the performance. You can get neat tablet holders that attach to mike stands and are quite discrete.

Personally, I don't use anything like that, largely because I'm far too vain to appear on stage with my glasses on, so I've got no choice to learn everything. Of course, being human, there is the odd slip up, but how you handle that is down to stagecraft, a favourite line of mine is to tell the audience that if they really want to know what happens in verse 3, they will just have to buy a CD!

very valid points from EBarnacle above, why is using words/music acceptable in some styles and not in others?

John