I use Kohana myself, for exactly the reason that you mention you like Zend - it's a good starting point. And if I need to extend Kohana's model or rewrite it f

I use Kohana myself, for exactly the reason that you mention you like Zend - it's a good starting point. And if I need to extend Kohana's model or rewrite it from the ground up, this is totally accepted and even encouraged by the framework. I find it's just way, way easier to get up to speed with a framework as a base, and if your framework is any good, then it should be easy to shove aside later when you need to special-case things for performance or whatever.