Funny how Matt Cutts was all over the Rap Genius article on HN right after it came out and he's nowhere to be found here. Must be the millions Expedia spends on Adwords, or my cynicism, one of the two.
you haven't lived until you've put pdb statements directly on a production machine and kept restarting the web server to catch a bug after days trying to catch it the normal way.
While this is actually really awesome, I think a lot of the nastiness of JS can be dealt with by using a good JSHint plugin for your text editor (that highlights errors/etc as they happen). Hoisting, function scope, ==, var, using variables without defining them, etc - it'll catch many things.