I have been doing a lot of development lately using the EXTJS framework. I have been setting it up to consume JSON from Web Services I have been setting up.
At first it was cumbersome to even get some basic administrative tools setup and working. The more I setup the fast it gets though.
I am creating various basic controls that are pre-configured to just ping a CFC and get their data. It works pretty smooth.
And I must say I am really enjoying not screwing around with an of the visual of a site. Its all consistently basic ExtJS styles. I could style out more if I wanted to.
I have never been the best UI developer, I get the business and back-end layers better. I know what makes a good interface, it is hard to just create the CSS and Graphics for it. So I really enjoy EXTJS. It helps me make a consistent and usable administrative system. With the different panels and controls you can really mix and match and make some sweet tools.