I will allow that there are some nice features, like first-class functions. And it facilitates jQuery, which is very nice. But for proper object-oriented programming it's pretty much fucked. And its array handling is a hideous nightmare. And jQuery lacks the array handling niceties of Prototype.js, and Scriptaculous lacks 99% of what's in jQuery UI and associated plug-ins.
If the W3C and the browser people could get their acts together and unleash Javascript 2.0 on the world, we might be getting somewhere. But I have no faith that this will ever come to pass.