There's a slide deck over at the Mozilla deverloper site that covers some of the changes/additions/bugfixes to be found in JavaScript 2.  It's interesting and worth taking a look.

With IE7 just out the door, I wonder if JS2 will ever really take off.  Certainly, if Microsoft decides that they have no interest in JS2--and a good question is why would they have interest in JS2 if XAML with .Net is superior, in their minds--then it would end up excluding a large set of browsers and thus a large set of developers and users.

It remains to be seen how Microsoft continues to regularly update IE7.