To AbstractJavaScriptExtension or not to AbstractJavaScriptExtension

Hello,
This is a application design and implementation question given the new functionality available in Vaadin7 alpha3.

With AbstractJavaScriptExtension it seems fairly easy to integrate the functionality of a third party library, say jQuery-Flot, but I am wondering if there is a recommendation for when to use AbstractJavaScriptExtension and when to create a full add-on (AbstractExtension )? Is there a best practice recommendation yet?

Thanks