WP MVC is a full-fledged MVC framework, similar to CakePHP and Rails, that developers can use inside of WordPress.
WP MVC is a full-fledged MVC framework, but behind the scenes it uses existing WordPress functionality to lessen its footprint and better interface with the parent WordPress application. The developer will not need to know about much of this, though, and may merely treat it as another MVC framework. It draws on concepts and workflows from other MVC frameworks; Rails and CakePHP are the biggest influences, and you may see some of their naming conventions being used.
If there's functionality that you'd like to use that isn't implemented in the example plugins or mentioned on wpmvc.org, it may not exist yet. However, if it's something that is widely useful, I'd certainly be willing to implement it myself or to accept any well-written code that implements it. Please feel free to either add a topic in the WordPress forum or contact me through GitHub for any such requests: