Advice needed - Best Ajax UI Frameworks?

[eluser]Randy Casburn[/eluser]
I keep finding myself coming back to ExtJS. It integrates seamlessly with CI requiring virtually no spaghetti code at all. It allows me to build standalone desktop apps using it's (almost complete) Adobe Air interface API that I then tie back to my CI provided web (SOAP / REST) services. The downside is that ExtJS demands you have a strong understanding of JS OO principles. Otherwise it can be down right ornery ;-).

Hope this is helpful,

Randy