[eluser]someone1[/eluser]
I've used Symfony, Zend, CakePHP and a few others and I always fall back on Code Igniter.
Although Code Igniter doesn't come with a lot of cool libraries prebuilt, you end up spending more time learning those cool libraries and work around them versus them working for you.
I think code igniter lets you code the way you want without the need for conforming to the coding styles of the creators of the framework. Its a very loose MVC structure and can be extremely powerful in the right hands. I think no matter the size of the project code igniter is a great choice. And you can always hook up with other frameworks to utilize their advantages, like integrating the ZEND libraries with code igniter so you get the lightweight speed of CI and the complete libraries of ZEND to handle what ever you need at the times you need it.
I for one use Symfony's methodology for templates in my projects as I think it makes a lot of sense in my CI projects, although i have to work a tad bit harder than in Symfony for it, the end result is still highly customizable and well structured.
Just my 2 cents!