It’s interesting to me how much [Closure] feels like a more advanced version of Dojo in many ways. There’s a familiar package system, the widgets are significantly more mature, and Julie and Ojan’s Editor component rocks. The APIs will feel familiar (if verbose) to Dojo users, the class hierarchies seem natural, and Closure even uses Acme, the Dojo CSS selector engine.
I think you overstate the usefulness of the [jQuery Rules] plugin. Using this plugin, users are now limited by what selectors that can use (they can only use what the browsers provide—and are at the mercy of the cross-browser bugs that are there) which is a huge problem. Not to mention that it encourages the un-separation of markup/css/js.