The fact that a non-programmer could fail to use TT successfully does not mean that it isn't easy for non-programmers to use TT. It means that it is possible for non-programmers to mess TT up.

I talked about this in Re (tilly) 6: Code Critique. The problem is fundamentally an issue of figuring out how you'll cooperate. If you just threw a bunch of templates over the wall to the designer, I'd expect a bad result. If the necessary communication and understandings were worked out for cooperation to happen succesfully, good results are possible (and many people have achieved them).