Wow, first Yui 2.3.0 and now Extjs 1.1!
This is the first stable released not mandating the use of a third party library (YUI, prototype or jquery) which gives a way to have a smaller size for the base library to download in a web page to use Ext's power.
The HTML editor is also a big addition to the library.
I've already been using 1.1 beta in production, and it was really solid and enabled me to build really advanced features very rapidly. And as I'm not a designer, Extjs' good look by default is really a strong point for me (Have you seen the layouts possibilities available?).
If you haven't made your choice on which Ajax library to use, take a look at Extjs! You get flexible data sources (reading XML, JSON) that you can use in different widgets (grid, combo box), layout facilities to build desktop-like apps, localisation, inline editing grids and lots of other widgets, a fast CSS selector, great documentation, active community to ask and reply to questions, user developed extensions, etc....
Congrats to Jack Slocum and all contributors for this excellent release. Looking forward to what Ext 2.0 will bring us!