I am seeking a solid framework to develop a website, and possibly other projects such as add-ons. Symfony was recommended and I wanted to ask the community if any developers were familiar with the software and had any feedback to share.
I've heard good thing about symfony, especially it's upcoming 2.0 branch; however, I haven't used it myself. I suppose it depends what exactly you are looking for.
Right now, I'm using Zend Framework as the underlying architecture for my current project. Although I'm please for the most part, I'm not too satisfied with its modular approach. But if you just need some components to save time, Zend Framework is really easy to adopt in that regard.
I've never used symfony. However, if your developing add-ons... Use Zend. Its part of the core software, and will make everything so much better for yourself in the long run. It may take a bit to get used to the ropes, but its better for XenForo.