What are the best/more stable features of the Google Closure Library

In November 2009 Google announced the release of Closure Tools which include the Closure Library.

According to this post google closure library contai开发者_C百科ns some battle-hardened parts and others more experimental.

Could folks with experience using google closure share info on which parts are solid and which are iffy(er) or not ready for production use? Some demos apparently don't work in latest firefox (as of January 2010).

The Closure Library is a JavaScript library that's

• well-tested by Google
• modular by design
• cross-browser compatible (very handy to save some hours)
• A large set of reusable UI widgets and controls
• sports performance gains in page speed

Lower-level utilities for

• DOM manipulation
• server communication
• animation
• data structures
• unit testing
• rich-text editing

Basically the compiler portion compresses your JavaScript logic into smaller code area that is compatible with a wide array of browsers, removes dead code, etc.

The Closure Inspector, a tool that makes it easy to use the Firebug JavaScript debugger with the Compiler's output.

And you basically get a good portion of what Google needs for itself to develop with - I love all these features.

I'm not convinced that what we need is another javascript library.

The compiler -- on the other hand -- is something we really do need, in large projects the javascript can begin to get quite unwieldy. Having a compiler that can cull dead code and tell you where it is will be quite helpful.