Have you checked my previous article on CakePHP…

http://blog.svnlabs.com/2009/11/cakephp-in-svnlabs/

Yii (Yes, it is) — a high-performance component-based PHP framework best for developing large-scale Web applications. Yii have features, including MVC, DAO/ActiveRecord, I18N/L10N, caching, jQuery-based AJAX support, authentication and role-based access control, scaffolding, input validation, widgets, events, theming, Web services, and so on. Written in strict OOP, Yii is easy to use and is extremely flexible and extensible.

YII Features:

- Magic overloading functions
- Lazy loading
- Authentication / Validation
- Widgets (sharing extensions)
- Yii console
- High-performance
- Templates
- MVC Push-Pull
- RBAC
- Test Case (PHPUnit, Selenium)
- EAccelerator
- jQuery
- Zend support

I am currently reviewing YII in comparison with CakePHP … Keep in touch