I have used Symfony for my last few projects. I'm happy with the way the framework is designed, and it's quite longstanding. Another benefit is the templating is done using pure PHP, so you don't have to learn a new templating language for loops, etc. A new version (v2.0) is due to come out later this year.

The introductory documentation and tutorial are excellent. The Jobeet tutorial walks you through how to create an entire application, with the Symfony developers' best practices being implemented right from the start.

Only con: I do have trouble at times finding answers to the obscure questions I have. There seem to be a lot of forum threads about Symfony, but not quite so many answers. If you can find an experienced Symfony developer, I highly recommend talking to them and getting a few pointers in the right direction. That said, I think it's a great framework, a little on the old side in terms of style, but still quite flexible.

CodeIgniter is fairly decent. I'm using http://fuelphp.com/ these days, which is similar but newer.

I also go back and forth between framework and homegrown. I've done homegrown for years. Framework does have the advantage that you get to use a lot of code others spent time on, so I'm sticking with that for now.

I dislike the Yii approach (it generates code based on your db). Don't think it's necessary, I have no problem coding and optimizing some mysql queries, no need to hide that behind a black box.

After going through CodeIgniter, Zend Framework and CakePHP, I'm pretty much exclusively using Yii for my own projects these days.

The way Components and Behaviours are used throughout the system makes it very easy to combine and plug in disparate modules of code, and it's the most Rails-y framework I've found so far (barring CakePHP which appears to have come leaps and bounds in the last couple of years since I used it last).

(In summary, it matches how I want to work. :) Keep looking until you find something that does the same for you.)