Advice needed - Best Ajax UI Frameworks?

[eluser]Unknown[/eluser]
[quote author="nmweb" date="1214137342"]Take care of licensing issues with ExtJS. There was a fuzz about it a while ago but I don't know the current status. jQuery UI is promising but not yet mature I think.[/quote]

Yep, there is too much uncertiny around that, I started out using ext but after the lic changes I dropped it, now I use jQuery or YUI...

the official jQuery UI is not mature, but there are plenty of high quality jQuery plugins out there