Yeah - back when coffeescript was new this was an argument, but with "use strict", the likelihood of accidental mis-assignments is actually considerably slower in javascript than in coffeescript. In javascript you'll get an error assigning to a non-existant variable you meant to be global; in coffeescript you'll get a local varaible and that means subtly buggy code.
I think cursork was talking about 'use strict' in Perl; he said that everyone uses it. 'use strict' in JavaScript is much rarer than it is in Perl, at least in my experience.
Well, I always use it when I have the chance: it's easy to turn on, and it catches nasty bugs. Why wouldn't you turn it on? Even if you have a large legacy code base, it's still a a win, since you can turn it on function-by-function.
