fast and server friendly via lazy-load
Interface is fast as most of the content is loaded via AJAX, when content is requested by the user. No costly preloading. In addition most of the content delivery interface part is rendered by client (jQuery UI dialogs), so it is server resources friendly.
Interface uses jQuery UI dialogs to display content. jQuery UI dialogs are not your simple popups. They are stackable, draggable, positionable, pinnable and highly flexible in every way necessary. They are adjusted to hold any type of content: paging, images, forms (powered by another plugin allowing auto-serialization) etc. Additionally the dialog interface element is auto-generated - so one click and it is ready for content. Dialogs are seamlessly integrated with other interface elements by specifically designed for this purpose plugin, which offers over a dozen different settings. 3D means that the page loads only necessary content and all of the rest can be loaded in dialogs, without needing to reload a page or load another. Dialogs are stackable in layers. All lazy-loaded of course, with a client generated interface.
bandwidth friendly, localized action - most functions are built-in or easily attainable
By localized action I mean that you can POST form and only form will be reloaded and output displayed - process is aided by FMVC and simple to accomplish. Same applies to any other local action, like some other content pull, local paging etc.
Main interface template holds location slots, so it can be easily equipped with e.g. Smarty or other templating systems. It uses jQuery UI, so themes can be applied. Dialogs are also extremely styleable - if instead of squares, you want your pops circle-like - no problem. All you need is some css.