We started our current project using jQuery/jQuery UI and I found that it didn't feel up to the task. We're creating a complex single page application with many

We started our current project using jQuery/jQuery UI and I found that it didn't feel up to the task. We're creating a complex single page application with many controls, etc. Things like menus, tree controls, etc, just don't exist in standard jQuery UI. And the plugins were mostly unsupported. I got up and running with the Closure library, very quickly, and I'm still finding it nice to use.