Never present a power-user option in such a way that normal users must learn all about it in order to know they don't need to use it.

It's hard to read through a book on the principles of magic without glancing at the cover periodically to make sure it isn't a book on software design.

If you are demanding registration before checkout, you need to cease this practice immediately. It is costing you a fortune.

The only intuitive interface is the nipple. Everything else is learned.

Never present a power-user option in such a way that normal users must learn all about it in order to know they don't need to use it.

As for the Sun mouse, I'm not a big multi-button mouse fan, because I just can't remember which button to push when. I rather like the Macintosh system of using four modifier keys with the mouse.

Constrain the user's expectations to match the abilities of the software.