[andreyf]

This is very impressive from a tech perspective, but what exactly does it have that native Cocoa apps don't?

[orib]

A browser window.

This is a Javascript wrapper, which means that browsers can execute it. Browsers can't execute Objective C.

I'm not sure why these people felt they needed a wrapper around Javascript, which already has it's own fairly dynamic object model, but meh.

[edit: elaborate a bit]