Object-oriented programming with Wordpress: utopia?

A long debate among Wordpress developers is essentially about the possibility of using truly object-oriented code in their themes and plugins by exploiting the latest features of PHP 5. Most developers who don't are accustomed to OOP in PHP think that OOP in Wordpress is rather difficult to accomplish and, in a certain sense, even counterproductive. But if you take a closer look at the inner structure of the Wordpress core, you'll surely notice the abundance of classes and most of the OOP features we're all used to see in other frameworks. This post is written in the hope of stimulating a renewed interest in OOP with Wordpress.