Totally, but if they are running under strict and warnings with lexically scoped variables, I actually have a snowball in hell's chance of understanding the structure of the code and refactoring as needed. I don't need to know whether they understand all the benefits - it's just that they will have already done the basic work of catching that variable typo etc before I hit it :)

That's a lot easier than trying to add "use strict" to a few thousand lines of code that have never run under strict before!