I'm not sure about this.

One of my favorite tools is my bicycle. To me, the user interface of my bicycle is totally invisible. I just pull it out of the garage, hop on, and away I go. And it's not like I enjoy my bicycle as a "puzzle" either -- I just want it to go somewhere.

But to my 6 year old, the user interface is quite literally fear-inducing. Everything about the tool is very "visible" to him. Does that make it a bad tool?